Ok, download and install Ccleaner (previously named CrapCleaner).
Just be careful to go for the free one. Very easy to install.
It has a facility for uninstalling any software you don't need any more.
Also, most importantly, it has a "Registry" cleaner.
You can also fillet your "Start-up" procedure. That's where a lot of sluggishness comes from.
Best of all, do a full "Analyse", and tell it to clear out any accumulated rubbish.
Your data would be safe.