My knowledge of computers is such that I just barely understood your last post, and half of this thread before it is complete double-Dutch to me. Luckily my roommate counts building computers from scratch as one of his hobbies, and went "I get to build a computer... but don't have to pay for the parts?? Yay!!! \o/" when I asked if he wants to help me out. =P

 Yea, if you want the most for your money, building your own is going to be your best bet. I recently put about $350 in upgrading my Ram, CPU, and motherboard. While I still have the same old video card, I now get the maximum performance that card is ever going to see. 

Before, Battlefield 2 at full settings would run around 30-40fps for the most part and up to 80fps in other areas. Now it runs 100fps almost all the time.

I have a Core 2 Duo E6400 overclocked to 2.8GHz, I got 2GB Ram and a 256MB 7600GT, and Crysis runs absolutely horrible unless all settings are at 'Low', and at that point there isn't much point in playing it because Far Cry does actually look better when you reach that stage!

I know the 7600 is ageing now but I'm surprised at the poor performance considering how well CoD4 and UT3 ran for me, I was hoping to get a 'little' visual flare out of this.

MrMarc: What resolution are you playing it? I played it with my other computer it got core 2 E6400 2.13ghz 2GB ram and 7950gt and I played it in medium. Nothing overclocked.

At 1440x900 with everything on Low it ran absolutely fine, but quickly became sluggish going on unplayable if I tweaked anything higher. Even when I ran at 800x600 with the visuals on Medium it ran like crap! :(

I played on all medium settings with 800x600. My PC is an e2160 overclocked to 3.0ghz and a 7800gt (256) and I averaged around 30 fps with areas going lower to around 15 (happens more in cut-scenes and when a lot of things are going on during gameplay).

lol, I noticed the similarity to Far Cry to with lower settings. I thought that was only me.

Far Cry DEFINITELY looks better than Crysis on it's lower settings though :P

 Please do yourself a favor and get involved with your friend while he builds it.  Have him explain the basics so you can build it yourself in the future if he isn't around.  It will save you tons of cash.

This will sound complicated but it really isn't! The big things are...

1) Know the essential parts of a computer (ie Power Supply, Motherboard, Processor, RAM, Hard Drive, Video Card).  Motherboards today come with sound and video built in to the motherboard and generally "onboard" sound is good enough to use if you aren't picky but "onboard" video is only used as a fall back in case your real video card is having issues.

2) Know where each of those parts goes in the case.

3) Know how each of those parts is connected or not connected by cables etc...to other parts of the computer.

4) learn how to look in the motherboard manual for the front panel jumper settings and how to properly connect the front panel to the motherboard

5) for a gaming rig understand the dynamics of airflow and that the basic concept is to suck air into the front of the case and blow it out the back of the case thus creating a single direction of airflow through the case.

6) Everything beyond that is extra and there is a lot of extra you can pick up. 

I don't know how experienced your roomate is but it sounds like he is quite capable so you should be just fine.  But if you guys have any questions please feel free to ask. 

can i play the demo on atleast low settings???

here are my PC specs (it is not really a gaming PC, im not really a PC gamer)

runs at: 1.6 ghz

vista home premium (32 bit)

intel (r) g33/g31 graphics accelerator

 You will probably need something better than onboard video to the play the game, though I am not 100% sure, you very well might be able to play it but I would imagine you would be getting crap framerates even at low.

Investing in even a mediocre card would likely increase performance as the G33 is primarly intended for office use.