Is my comp dead??

This is actually one of my older computer I am talking about. The CPU and mainboard has been used for approx. 5 years. I also remember overclocking for about several months then stopped overclocking and set it back to original speed.

Here are my system specs:

*ASUS K7V Slot A motherboard VIA KX133 chipset
*AMD Athlon 800MHZ (4 years after I overclocked it to 840MHZ for a few months
then switched it back to 800MHZ due to stability problems with some games.)
*Forsa nvdia Geforce 32MB
*128MB SDRAM generic
*4GB HD
*generic floppy drive
*NEC 2x CDROM
*Windows XP professional

Here is what happened. I turned on my computer one day and right when it tries to boot windows I get a blue screen saying: IRQ NOT EQUAL.

I tried to reinstall XP. same thing happens. format works though. I formatted clean partition and still gets the samething.

I tried replacing the RAM but after replacing chip modules and shifting locations and placements of the modules several times, I begin to wonder if it is the mainboard and cpu??

A few days later something even worse happened, my comp can't seem to process I/O signals from keyboard properly. such as some keys not working at all. I used a fully functional keyboard from a working computer and got the same result.

so in short my computer cannot:
1) load windows
2) boot windows os
3) install windows
4) all keyboards start acting weird when using on this comp.

Is it very usual that computers break down after 5 years??