I'm a little late here
Sorry jon
Yes the first thing is to sort out your system, as you seem to have done, clearing the reg, old files, deleting unused programs, and doing anything that will spped up your disks operation like defragmentation etc.
Then you can have a little go at sorting out your operating system, clearing out any processes that are useless, tweaking certain settings that can speed things up a little.
Caution over overclocking though ... overclocking creates heat ... the death of silicon, so unless you have suitable heatsinks and fans, then I would advise against anything drastic. A little can be gained with simple overclocking, although, I doubt you would notice much difference. Often more speed can be gained by simply slapping in another stick of Ram!
If you need to know more, I'll post more details if you want
