Yeah, get rid of all spyware, definitely - see in my first post about Spybot Search & Destroy, and Malwarebytes Anti-Malware.
I've never heard of PC Pitstop, though looking at the website it looks like it's worth a try. From the sound of it, the Driver Scanner certainly sounds worth using - one thing I forgot to mention is to install all the latest drivers, you can quite often get a bit more performance from more recent drivers - especially chipset and GPU. If you do try it, please report back if it's any good
Registry Mechanic, also never heard of it, but I imagine it's a registry cleaner like the one on CCleaner.
There is one other possibility, which is to update your BIOS; this isn't something the average user should do though.
I really need to piece together a 'How to speed up your system' guide. We get this sort of question fairly often :P