The System admin set policies to prevent installation?

Hello! I have used to have Smart FTP installed, but because there was an error with uninstalling, there are some rogue files and registries on my computer. I have managed to remove every key and file I can find, and now, the program is gone from my computer. However, when I tried installing again, the following error appeared:

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The wierd part is, I'm the only system administrator on the computer! I'm using Windows XP.

I DID find a key couple of keys inside the registry that I have not made a backup of, and they were called something like "Authorized Policy" or something. Maybe it has something to do with it? Right now, it doesn't bother me that much... except for only the fact that I can't reinstall SmartFTP... Can someone help me please, because coreFTP is really bad...

Thank you!