dad,s computer wont boot

every time it tries to boot, it does a memory test and fails.it always continues, but never gets past the verify dmi pool data screen.whats going on?

edit:bios is detecting only 512mb of ram.it has 2 sticks of 512mb ram in it!

reseat both sticks. Then try 1 stick at a time, see if one is bad.

sticks were covered in dust! tried just the stick with the least dust (after removal of dust of course.) it booted and im yet to turn it off.will find out tomorrow weather it will boot with both sticks.