Before you download anything do the following maintenence to your computer (If you don't already do so :p):
1. Regularly defrag your system (This will take a while)
2. Use the disk cleanup tool (found in system tools)
3. Remove temp internet files regularly. (although the disk cleanup tool should do this).
4. Remove unecessary tasks that are running on startup. This can be a little more complicated than the above. Not sure if you're using Vista/Xp or another operating system so could be a few ways how you access it. When you get on the page it will list a load of tasks and tell you whether they are automatically starting up or not. Simple change them so unecessary programs aren't starting up when you boot up your system.
5. Turn any visual themes you have on, off.
As for downloadable programs, I have a disk defragmentation tool called "Auslogics Disk Defrag" which runs more efficiently then the Windows counterpart at comes up with a message at the end saying something like "your system is 7% quicker" (Although I don't know how accurate it is :D)
You said you have Spybot, if you don't have them already try Adaware/Bazooka Spyware/Super Anti-pyware.
I'm not aware of many other programs that can magically speed up your computer, most of them seem like cons to me :p
Good luck with it anyway Scotty ;)
