Download and install:
CCleaner ->
CCleaner - Optimization and Cleaning - Free Download
Auslogics Disk Defrag ->
Disk Defrag - Fast and Safe Defragmenter for Your Disks
Remember to run them as administrator. Yes, do a registry backup when using CCleaner.
A little cleaning can help lots.
Also before running those, uninstall any programs you're not using. Get rid of files in your 'my documents' folder you're not using or haven't used in a long time.
Just out of curiosity, how much Hard-Drive space do you have used/available?