Trying to upgrade Compaq Presario into mid-end gaming machine

Hello guys,
I just joined with this site today because of the noticably large community.
I want to play some of the newer games out, but i cannot do this because my computer is kind of outdated (and crappy).

I need to know what major hardware upgrades I should get to be able to play some visually demanding games like FarCry and SC2.

All my computer specs are in the link below.
http://h10025.www1.hp.com/ewfrf/wc [...] R1002_IEEN

Tell me what needs to be upgraded in order of importance.

Thanks.

Here's what I can find:

Best CPU supported: AMD Athlon64 3800+ (not good enough for most modern games)
Max RAM: 2 GB (ok)
300 Watt PSU (can support decent graphics card, but nothing too serious for gamers)
(1) PCIe 16x slot (good, but limited by PSU)

I'm 99.999% sure it's not worth upgrading, but if you want to try, please post which CPU is installed in the machine and how much RAM you have.

In all honesty, the only thing left standing might be the case (if its not a BTX . . . er, if its a "non-standard" case) and perhaps the modem, though I don't know if you use that.

The power supply is too small, the motherboard BIOS controlled by HP is too restrictive for cpu upgrades. The 120GB hard drive could be usable as a secondary storage device. But the CD-writer/DVDROM could warrant a $20 replacement if creating a DVD is on your agenda.

Further, even if a motherboard upgrade were possible, you probably don't have a true Windows Disk (you likely have a recovery disk) and so would need to buy a new OS as well.

These systems are designed by the manufacturers to be replaced, not upgraded.

OK,

Step 1: Install this or similar, and see if you can get it to run on your existing psu:

http://www.newegg.com/Product/Prod [...] -_-Product

Step 2: If it doesn't run, upgrade psu to this or similar quality:

http://www.newegg.com/Product/Prod [...] 6817371023

Unless restricted by your cpu/mobo, your gaming performance should be as shown here:

http://www.tomshardware.com/review [...] 697-2.html

Step 3: At some point either add another 512k stick of memory, or replace the existing one with 2x1GB.

If performance is not acceptable, your cpu/mobo will need to be replaced.

Before starting, figure out if the gaming performance the 4850 is capable of delivering is the target you want to shoot for.