Information high lye

My desktop computer keeps freezing up, could it be a power supply problem? - hobby power supply

I formatted, checked the cooling of CPU, hard disk, floppy disk, install the video card, basically everything apart and put it back together. I can not find the problem. I think it might be food, but before he did, I thought to look here and see if someone has an idea. Even if you reboot, sometimes will not start correctly. The screen is frozen and keyboard, but other elements seem to be always (hard and CD drives, flash cards). Internet access seems to be true too demanding. Some pages do not load at all.

It is a Dell Dimension 2300, approximately 5 years. I know it's a bit old, but it's almost like a hobby, try to make it run. It has a Pentium 4 2 GHz, 750 MB of RAM. I have it with 2 hard drives, but also one of the reasons why I think it may be a current problem, are affiliated with both drives, it will not. It has XP.

Any ideas would be welcome, thank you.