To keep a workstation functioning at it's optimum, what should be done on a regular basis and at what intervals?

Before I started using Tuneup Utilities 2008 for cleaning the registry (I disable 1 click maintenance), a nice defragment utility like Perfect Disk and an eraser like Eraser (free) or BcWipe to keep my free space clean (windows recycle bin deletes nothing), I used to have to reformat every 6 months or so because of system slow downs. Now I'm good for years. Ccleaner helps as well but I do not like its registry cleaner and Tuneup has never screwed me. There are newer versions of tuneup utilities but you can get the older 2008 for free if you look hard enough (mydigitallife) besides the newer versions got a little pushy and in your face unlike 2008.