Internal Error 2203 when installing software

About 2 months ago, I suddenly was unable to install some software and since then, many programs give me this 2203 error. I've read that it's about permissions, and if I go into the Admin account, I can install the software. This is annoying but I could live with it. Yesterday, however, I did that for AutoCAD and I can't even open the program in my user account, which has admin privileges. I can't live with this. I've tried all the suggestions on various forums for this error, but nothing has worked. For example, in my user a/c, if I open cmd as as administrator and start the exe file for AutoCAD, I still can't open the program. I've tried giving the folder with the executive file full control, and that doesn't help either.

Any suggestions? I really need to solve the original problem that I'm getting the 2203 error when I install software with my user account.
Thanks,

I don't know what the problem is. All I can tell you is that error number is equivalent to "the password parameter is invalid." Do you have an Admin account without a password?

One quick thing you could try is create a new user account and see if you can install the app and launch it from there. If there's a registration issue with the software license you might contact the software publisher and explain your problem.

Yes, I have an administrator account without a password. Should I add one? Do you think that would help? My user account does have a password.

I'm hesitating to contact the software publisher because the problem happens with most software packages, so I KNOW it isn't their problem.

I know I had trouble with XP. If I tried to run a program as administrator, because my account didn't have a password. It wouldn't do it if I left it blank. I added a password to my administrator account. Then I could do it.

I'm not suggesting you go to the publisher for support. Only if the program has a registration that might prevent you from installing to a different user account. They might in that case give you another product key for instance.