Hi asrok.
Please follow this link so can get some good information of How to run defrag in safe mode.
http://technetDOTmicrosoftDOTcom/en-us/magazine/ff458356.aspx (DOT is .)
For your second problem. Click on start run type mscofig and click on Services then MARK on Hide all microsoft services and hit disable all.. do the same with startups tab.. hit disable all of them and restart your computer. Check do you find any improvement.
Try Ccleaner and clean junk, temps and unwanted things this really helps when your PC slow down.
Keep your computer upto date with microsoft updates.
Please update here your response.