|HP Pavilion a1120in specs: http://h10025.www1.hp.com/ewfrf/wc/...|
"i have installed 500 GB hard disk"
Is it a storage drive?
"i am using windows xp with 512 MB ram"
This isn't the cause of your problem but you should seriously consider adding more RAM, a LOT more RAM. Your system has 4 memory slots & can accept up to 4GB max (1GB per slot). If you have 2 slots available, I recommend added 2 x 1GB to bring the total up to 2.5GB. And if you're still using the crappy onboard video, I suggest you install a video card too. Unfortunately it looks like your board only has standard PCI slots - no AGP, no PCI-express.