Well tried installing an old version and I get a similar error - I've done a purge through the registry and deleted any dir's.
I guess I'll reboot and try again tonight.... The only thing I can think of is I didn't uninstall before the install I figure the package would do that for me... Maybe not cleanly...
Well I tried uninstalling v3.04 and clearing my cache. I looked around in the registry a little and didn't see anything obvious, but I'm not comfortable playing around in there so I left everything alone. I even restarted just in case that might help. Then I redownloaded the newest version (v3.051) and came up with the same error. I was thinking that the problem may have been fixed because the version I had problems with before was v3.05. Also, I don't use a download manager. Luckily I still had the setup file for v3.04 and it installs fine.
Yeah, I downloaded the CastleLinkInstall_3051.exe file to my Program Files folder and opened it from there, that's how I still had the v3.04 and v3.05 to reinstall.