How do I return my computer to factory blank after I have screwed it up royally?

I have a Dell running a Xeon processor and Windows XP. I decided I was tired of using Windows, and the constant problems (I’d been having graphics card driver issues causing screen of death episodes) so I decided to install Mandriva, and get my Linux flippers wet. That was the end. I ran the install disk on a separate partition, but it was never recognized on start up, but went straight into Windows every time. Things went downhill from there. The screen started flickering, and now on the boot screen, if the monitor is on at all, it is randomly substituting letters. Often a C for an S, like Windowc, or dick. The numbers have a tendency to be their corresponding symbols, like 1=!, 5=%, etc, although there are other less obvious subs. Also, ones, zeros and equal signs everywhere. Then the Windows emblem loads, runs through its start up, and then the screen goes black. I deleted the partition, reformatted and reinstalled windows on my primary drive, but it hasn’t changed anything. Anyone have any ideas or suggestions? If I could wipe the whole thing out and start over I would…