Photo Elements 5

I think somehow write protections or something else has happened to my C:
drive. After downloaded the free demo it gets to 99% unpacking to c:? drive
and then an error message occurs ( along the lines of check to see if you
can write and available space). I then changed some security settings so I
could write ( it now shows with a tick ) but still get the same message. So
I then changed the C to an e ( different drive )and it worked but program
gave an error. So I removed, manually dragged the unpacked files to C: drive
and ran the setup file. Well it worked and I can now get into the program
but now it says the demo period has expired.

Any suggestions ?