Please help me with my comp

I build a comp and it works really good for about 1 year but now there are some program that wont come up at all.

Like, when i go to Start>Accesories>Paint. I clicked the paint program but it wont come up. After i clicked the paint program from the start menu, the hour glass still there and my hard disk light was blinking but then it stoped and nothing come up.

This is the same when i go to Control Panel>System>Device Manager. The device manager window just wont come up at all but the hour glass still there indicating that its in process, then its stopped and nothing come up.

I have no idea wats wrong and this is really bothering me. So, some help would be appreciated. Thanks :wink: