If night_angel's solution doesn't free up enough space, you can also load Windows Explorer, make sure Details is checked under View at the top, browse through the E Drive's folders and look at the files that are there and how much space they are taking up. You may find some very large files that are no longer used. Right click on them to delete them.
Don't delete anything in a program folder unless you are 100% sure that it's a data file like a video file, not one used with a program. If you're not sure what's in the file, double click and see what loads. If nothing loads, I'd leave it alone.
Once you've done that, don't empty the recycle bin until you have tested any programs running out of that drive. You can restore the file from the recycle bin if there is a problem. Right click on the file and select 'Restore' if necessary.
I wouldn't suggest doing this on the C Drive anywhere except files under 'My Documents.'