I've got a list I've posted several times here on TF, but don't feel like looking it up.
Unistall anything you don't usee. Don't delete, uninstall it.
Download and use Spybot, Ad Aware, and Microsoft Defender. Make sure to update each one before you run it.
Do a virus scan with your antivirus, then do one with an online virus scanner (housecall.trendmicro.com
is a good one). Run CCleaner to clean out temp files and stuff. Then run it and use the Issues feature to clean up your registry.
Download and use O&O Disk Defragmenter. Both the freeware version and Pro version are available on majorgeeks.com
under Drive Utilities.
Finally, use MSCONFIG as jonny_uk said. By doing it last, you eliminate the need to have to do it twice. Once you reboot, check the box so the box doesn't pop up each time you reboot.