Since your computer is still decently new, I personally would not delete anything that you aren't sure what it is because those may be important system files. As for parts of programs still sitting around, try uninstalling those programs officially through the Control Panel. Good luck :)

Thanks quad, this fixed my problem!

I had this exact problem. I had a SigmaTel Audio. The switch from XP to Vista somehow corrupted my audio; I couldn't hear anything! I reinstalled the audio driver (it doesn't matter whether you dowload the one for vista [U]or[/U] xp, either will work since it is the vista installation, not the actual operating system which wasn't compatable w/ the audio driver.) from the dell website. After all of this, after it said there was audio coming out, there wasn't. So I simply tried using new speakers-and viola! Problem solved.
Also: I have a Dell Dimension E520. I now use Vista Home Premium.

From using the 'Dell Express Upgrade' from XP to Vista, it took me about an hour once I had all my files backed up. To log on and get all users set up, it took another half hour.

Thanks! I tried this and it worked. I've had this problem ever since I've switched to Vista Home Premium. I have a Dell Dimension E520. My cables were also on SATA 1 & 4. I moved them to 4&5. So far, for hours now, NO FREEZING! Again, thank you very much!