My Dell XPS with windows xp freezes after I log in and after it freezes a terrible buzzing sound is emitted from the tower until I restart my computer. I have scanned for viruses and spyware with avira AntiVir and found nothing. I don't know what is causing this! Any help would be greatly appreciated!

Is the buzzing sound coming from the internal speaker or from a device, such as fan blades hitting something?

No its coming from a small black knob thing that is on the motherboard I think?

What model XPS? Dell has full documentation on their web site to determine what conditions cause alarms beeps and buzzes. Also possiible if the black knob thingy is the internal speaker and a sound was playing through it when the system locked up, the sound can repeat.

It is a Dell XP 410 (XPS410GMSB) PC Desktop from 2006. It's the same sound every time a high pitch buzz.

Dell's documentation makes no mention of any audible alarms. Do the diagnostic lights indicate anything? Given the age of the machine, fan failure or power supply problems might be expected as potential issues. Suggest calling Dell tech support and see if they are aware of any audible alarms this system may generate.