If you've built your own PC, rounding up the pieces for a laptop and assembling it will not be a big deal. However, be forewarned:

What you get is a bunch of little plastic bags with tiny screws in them and two heatsinks - one for the CPU and one for the GPU. The Manual that ships with the laptop explains how to turn it on and what the buttons do - that's it. You have to figure out where these tiny screws go and how to shoehorn the heatsinks into place. The mechanically-challenged should avoid the barebones experience.

In my case, the ASUS C90S needed the following components:

• Desktop CPU
• Videocard
• Memory
• Hard Drive
• WiFi Card
• OS

A word on the CPU; ASUS will tell you that the E6320 is not supported - according to ASUS:

"The C90S supports Core 2 Duo (Conroe) "E4300, E6300, E6400, E6600, E6700, X6800". Core 2 Duo (Merom) NO, Core Duo (Yonah) NO, Pentium M (Dothan) NO, Celeron M NO. E6320 is a newer Conroe and unfortunately is not supported by the C90S."

I relate this because I found this out after I asked Directron for the E6320, as the spec sheet was not as specific on what CPUs are supported as my subsequent inquiry. As I found out, the E6320 will work fine as will the E2160. This is the fun part of the barebones experience - finding out what works and what doesn't (as an aside, I also found out that it runs without the battery installed).

For the RAM I decided to buy some cheapo PNY - I wanted to see if this would work and it did - no problem. The only other part was the hard drive and that's a no-brainer standard part. I did not use a WiFi card as I have sworn off wireless routers, so I can't add anything on that.

I had some questions and I called ASUS laptop tech support - it's available 24/7 and it's really true - I called on a Sunday night and got a live tech located in California. This was almost a jaw-dropping experience - no wait. However, you must accept that the more esoteric your question, the less likely you will get an answer. Let's face it - the techs can handle the routine stuff easily - anything that's outside the script is a crap shoot.

Even so, I was pleasantly surprised with ASUS tech support for laptops - nice guys trying their best to be helpful.

ASUS is marketing the C90S as an "overclocking laptop", so that's what I concentrated on trying out. I installed the OS (XP), booted into Windows and then installed all the drivers that ship with the C90S. The screen on the C90S is stunning - native resolution is 1680 x 1050; for some of the veterens among us, you may have to adjust text size - for me it was a bit too fine but setting text size larger fixed it.

The C90S is "certified" for Core 2 Duo E4300, 6300, 6400, 6600, 6700 and 6800. Naturally the first CPU I tried was an E6320 to see what else worked:

Booted up and ran fine - no problems. I would have thought this to be the case as it seems the only significant difference is the cache size - 4 MB vs 2 MB for the others. The Intel 945G Express Chipset supports FSBs of 533, 800 and 1066. On the off chance that somehow a pad-modded CPU to 1333 would work, I tried but no joy. As the chipset supports Pentium D, I tried that also but no joy on that one.

Next I decided to throw in an E2160 that I pad-modded to 1066 - this is the CPU that came with the Dell Vostro 200 that I reviewed HERE. I figured since the chipset supports 1066, this should work OK - and it did:

It ran reasonably cool at that speed as well:

Next I tried to overclock the E2160 using the ASUS overclocking utility - no matter what I did, I had no luck getting it to work. Based on some posts I have seen, this is not unusual. What did work was the power saver mode which dimmed the screen and slowed down the CPU. This is of limited use as you can get the same thing using a program like NHC.

I ran benchmarks to show how the ASUS stacked up against some other systems:

These benches are similar to PCs using an E6600 running at 2.4 GHz - no real surprise.

Software overclocking has a mixed record - sometimes it works great, sometimes it's a bust, sometimes it works but blue-screens under stress. As the basis for calling the ASUS C90S an "overclocking laptop", I'd have to say it's a stretch. I would not buy it based on the overclocking software utility that comes with it. I had expected to see more flexibility in BIOS, but sadly that's not the case - you can't vary FSBs or memory timings in this BIOS.

However, as a laptop that will easily accommodate pad-modded CPUs, the ASUS C90S is very easy to tweak. While the BIOS is a total bust as far as overclocking settings, the ease of getting into this laptop's system board far outweighs any other shortcomings. I can't stress this enough - anyone who had tried to clean a dust-clogged laptop cooler usually finds that getting to the CPU cooler involves MAJOR disassembly.

The other encouraging factor I found was that most likely all E series CPUs from the 2000 to 6000 series will work no problem in this laptop. I can't tell you that anything above 3 GHz will work, but it looks like the best bet is pad-modded 800 MHz FSB CPUs running at 1066 MHz at CPU frequencies below 3 GHz. As the E2000 and E4000 series are good buys on eBay, these can make a very nice, low cost alternative to something like an X6800.

One of the distressing features of many laptops is how warm/hot they run under normal use. Pushing the envelope by overclocking is going to result in a fair amount of heat generation, as the C90 uses desktop CPUs. This laptop features a complex of four fans - three directly tied to the CPU's temperature and one dedicated to the GPU.

The overarching problem facing all laptop designers is the miniscule footprint for a heatsink. The picture below compares Intel's retail heatsink for an E6300 to the ASUS heatsink:

While the ASUS looks like a cut above the norm, it still does not compare in fin area to Intel's desktop heatsink. Compared to a "tower" heatsink, it's downright anemic. It should come as no surprise that the heat coming out of this laptop's back could warm a small room. At a minimum, a good laptop cooler with a gasket (HERE) can go a long way to more effective cooling.

The GPU cooler sits on top of the videocard:

In use, I found under "normal" use that the fans were not at all noisy - even when they kicked on, they ran at low speed so that noise ws minimal. Frankly this surprised me as the fans are 12 volt Deltas that, at full bore, will be quite nosiy. One thing I would have liked to see in BIOS was a way to set at what temps the fans start to kick in - this is pre-set and not alterable in BIOS.

I ran some tests with a digital thermometer placing a thermocouple at the C90's exhaust port with the following results:

At first glance it may seem strange to see higher exhaust temps at idle, but at idle the fans are very low to off - almost passive cooling. Under stress the fans spin up, hence the lower exhaust temps reflecting cooling airflow through the fins.

The C90 features a built-in camera - rated at 2 MegaPixel, here's an example using the "snapshot" mode (640 x 480):

Not bad for what it is - nice coverage and an OK detail level.

Almost two years ago I reviewed the ASUS Z71A, another ASUS laptop that was very easy to overclock and to work on. I tried a number of mods on this one, including watercooling, and still use this every day as my main PC. Overall it's been a workhorse and has never been a problem for me.

The ASUS C90S looks like a worthy successor - it has a dynamite screen, is easy to work on and will accept a variety of pad-modded CPUs. The cooling complex with four fans is unusual but does the job - under normal use, the fans were not noisy; pushed, they will be, as they should.

The C90S is marketed as a DTR - I would not haul this around as a portable, but that's me (almost 7 pounds in my book is not a portable). As a DTR, I don't doubt that the more enterprising among us could easily mod the C90S for watercooling. As I demonstrated with the Z71A, it's very doable as long as portability can be sacrificed; after all, it is a DTR.

I give high marks to ASUS for 24/7 notebook tech support - I used it and got a real person on a Sunday evening!

Many many thanks to ASUS and Directron for their patience and support for this review.