As suggested you can set your pagesys file (virtual memory) to another drive.
You can also reduce the size of your recycling bin, default is 10% of drive and 1% works just as well (right click >> properties).
Also reduce the size of the system Restore allocation via Control Panel >> System default is often 10 to 14% anything over 200 MB is usually sufficient. If changing delete old restores first, button to do this with the restore settings window.
Also the default temp file store is usually c:\windows\temp you can create a temp file on another drive and reset the pointers in Control panel >> system >> advanced >> environment settings and the registry settings for each profile. NB delet the contents of the existing directory regardless of what you do about and same for the temp internet files one below.
Ditto the C:\windows\temporary Internet files it can be changed through MSIE Tools>> Internet Options >> Temp Internet Files 'Settings' button >> change folder.
If everything was in their default settings this should free up about 30% of the drive that you had not been able to use before.