How to clean up my computer?

I did i free scan from several site and i can not pay for none of the sites to fix my problems can anyone give me some free sites to fix my computer problems below
Registry errors, missing windows shortcuts errors, missing shared files errors, missing application path errors, missing font errors, missing help files errors, and invalid file extensions

If anyone can help it would be great but it must be free

it says "there’s no changes to restore", I check all this:

[ ] HKEY_CLASSES_ROOT
[ ] HKEY_CURRENT_USER
[ ] HKEY_LOCAL_MACHINE
[ ] HKEY_USERS
[ ] Start Menu Section
[ ] Obsolete Software
[ ] File Extensions
[ ] Add/Remove Programs
[ ] Shared DLLs
[ ] Fonts Section
[ ] Help File Paths
[ ] Uninstaller Entry
[ ] MRU History Lists
[ ] Empty Registry Keys

There’s something for "not to erase"?

I replace all but stel can’t restore system!

Is there a way to reactivate all the restore points (or marks)?

Thank you very much!!! See you!!!

I used a windows registry cleaner and ticked the boxes for all file extensions. Now I am not able to open any file. None of the file extensions are opening although the system starts normally. When I press CTRL+ALD+DLT, only the explorer is running. How do I restore my system. Please help me.
I am not able to open System restore from System tools as the lnk is not opening.