I was running out of space on my computer so I removed Elements 3 (I'm now using 7). When I went back into a video I'm editing in 7, all the letters in the section titles have turned into boxes. And when I try to type in new titles, more boxes appear. Can this have happened because of deleting Elements 3? Is there a fix for this apart from reinstalling both 3 and 7?
Deleting one should not affect the other. Though reinstalling 7 won't hurt.
Still, if you're that tight on hard drive space, you may be having other problems. The programs themselves only take up a few gigs of space. But, when they're running, they usually need between 20 and 30 gigs of free, defragmented C drive space for paging and scratch files.
If you haven't got at least 20-30 gigs of free, defragmented space on your C drive, the program isn't going to run right.