Question Re: Dell Diagnostics

Hi! I recently purchased a new Dell Inspiron (the service tag of which doesn't show up in search, but that's not THIS issue) because my old one was acting wonky. As usually happens, as soon as I got the new one home the other got "better"...for about a week. This week I had been randomly losing mouse and keyboard and this morning I was watching a video (not online, but on the harddrive) and everything froze! I ran all sorts of tests: malware, rootkits, did dskchks, a system restore, and even almost re-installed Vista, until I realized my dvd does not have a "repair" option, and I didn't want to lose everything, as I haven't fully migrated to the new computer. Nothing worked completely, and I was back to losing my mouse/keyboard, which, through testing, I attributed to my usb ports not working. So I downloaded the Dell Diagnostic and that seemed to have worked. But I cannot find results to know what might have been fixed or what might need repair/replacement.

 I just tried to access the older Dell with a flashdrive and it froze again, so apparently not fully fixed.

The computer I am having the problem with is a Dell Inspiron 530 . Pentium Dual Core 2.5 GHz 4.0 GB Ram and 32-bit.

I'd welcome any suggestions. I've exhausted my knowledge. I have very limited funds, but hate to give up on a computer that was working until recently. Thanks!