This is a question that constantly gets asked, that and can I install Sonar x (meaning the newest version) along side the existing version.
The answer is: install the latest version, BUT don't touch the old versions.
You "hosed" your plugs when you uninstalled version 8.
You have space issues, and that's the ONLY reason to uninstall.
Sonar installs its own "bloatware"; demos, loops, that sort of stuff.
Go into pref's, file locations, and find where all that got put.
There's probably a "user" folder for each version, that crap can go.
Alexs is right about a fresh Win install, PITA but that's probably your best bet...
Backup any "presets" and track templates you've saved first!
Tom