OT: Desktop comp writes by itself, what might be wrong?

Hey guys, sorry for writing this in the aspire one forum but it's the only foru§m I'm a member of.
I have a really weird problem on my desktop computer (Asus K8N4-E deluxe motherboard, regular ps/2 keyboard, Geforce 6600 graphics card)
I first noticed it shortly after installing some Nvidia software to overclock my crappy 6600 gpu. I'm not sure if that is a coincidence or if it's related.

The problem is, my computer randomly spits out these guys §§§§§§§ (with shift it becomes ½½½½½)
It doesn't seem to be a keyboard issue since when I tried unplugging the keyboard it actually got worse (several § per second instead of one § every few seconds)
It also doesn't seem to be a virus issue since the same happens when I boot into bios setup.
Have I somehow screwed my hardware when experimenting with overclocking?
Any ideas? I'd be really greatful for any help since I really can't afford new hardware.

 

T§o i§§§§§§§§§§l§lustrate the issue thi§s is wha§t happ§ens wh§e§n §I tr§§y to write§ with§ou§t §erasing the §signs that§ ap§pear§