Error 1303 when installing Graphics Suite X5

I'm trying to install a trial version of Graphics Suite X5 onto my computer. I currently have X3, and this is on Vista. I am getting:

 Error 1303. The Installer has insufficient privileges to access this directory: C\Program Files\Common Files\Corel\Shared\Shell Extension. The installation cannot continue. Log on as Administrator or contact your system administator.

What do I do? I saw a similar problem on here for Version 12 in a search, tried the solution posted for that, and that didn't work.

Any help is appreciated!