LittleMissMiley,
Just got home from work. I missed a bunch of threads, but if you seriously considering getting a new rig, think long and hard before building one. I built mine and I've been doing it for over a decade. i don't know what your money situation is, but name brand PCs have come down A LOT over the last 5 years, due to changes made during the manufacturing process and cheap labor. Truth be told, if you don't plan out a custom build right, it is very easy to end up spending more then going to a store.
That was kind of why I asked about the beeps earlier on. It is actually a code that tells you what's wrong. The guide for that is here: http://www.nullamatix.com/dell-diagn...hooting-chart/
It could be that you have a component that is failing, or just a connection was loose or dirty.
Did you mean he has a quad core or a Pentium 4? If you meant Pentium 4, it won't run the game. The minimum requirement is a Core 2 Duo.
I apologize for not understanding your situation better earlier. It would appear your only option will be to buy a "newer" system, as you old computer would not meet the requirements to play the game, even if it was working perfectly.
That said, if you still want to fix it, I would suggest checking all the connection inside and maybe cleaning out some of the dust. Needless to say, make sure the power is unplugged and wait for it to completely dry out before plugging the power back in, if you use any liquid cleaning agents.
Pentium 4s are almost a decade old. Any mobo with a P4 socket, is probably going to support DDR1 RAM and AGP/PCI GPUs. The most you'll get out of it gaming wise is Quake 3.