Need help rebuilding a PC for gaming

Okay, so I had these two old HP microtowers: one of which I had used for music programs and a small amount of gaming and the other for school-related stuff. One day, the motherboard for music and gaming microtower died and wouldn't come on no matter what i did. Also, I bought it from someone I knew, hence no warranty. That's when I decided to completely gut it, put what I could on to my other one (which I'm currently using) and keep the frame. So, any ideas?

Here's some more info that might prove helpful...

General Info about the microtower.


Specs when I first got both

OS: Windows XP SP2 Professional 32-bit
RAM: 512 MB
GPU: Pentium 4 3.0 Ghz
Graphics: ATI Radeon Express 200
Hard Drive: Seagate Barracuda 80GB SATA

Then, when my cousin moved, he gave me all of his old, non-working computers, and I used some parts from those to build the media computer up to this...

Media Computer specs after adding parts and before the motherboard died

OS: Windows 7 Ultimate 64-bit
RAM: 2.5 GB
GPU: Pentium 4 HT 3.2 GHz
Graphics: ATI Radeon x300 series
Hardrive: Seagate ST340015A 40 GB IDE (OS only), two Maxtor MaXLine Plus II 250 GB SATA's (games), 500 GB LaCie Rikiki USB External (everything else)

Have you tried reading this?

Additionally, I hope you realize in many situations the case is probably your least expensive component, so unless you have something else you want to salvage you might as well just build a new machine entirely.

Sorry, didn't pay attention to that.

Besides, the only things I could salvage were the RAM and hard drives so I'll try building a new one and probably use those parts.

Thanks!

Check out the 'How Good is this?" thread like 2 below this one, theres a great deal on a barebones kit. Looking at the specs of your old computers, its already a pretty good improvement. I say scrap the old case, but I guess if you REALLY want to you don't have to.