you could take a look in
Control Panel/Administrative Tools/Services
and see if there is any junk or stuff enabled that you obviously never use. I know i-Tunes causes a slow startup and so can antivirus and content scanning filters.
Be careful what you disable in Services though, it you don't know what it is, look up in Google and tend to leave alone rather than disable!
Doing CTRL Alt Delete and looking at Processes in Task manager, also looking up on Google helps give clues what junk might be cluttering up your PC