[DeFault User]

If all else fails, make a list of hardware drivers needed, make sure you have installation disks/programs, backup any data you want to keep,reformat the HD and load a fresh version of the OS.

This is drastic but cures a lot of problems.

[SealSeven]

If your wondering what some of those start-up programs are, go to this site:
http://www.pacs-portal.co.uk/startup_pages/startup_full.htm