Helping people with computers... one answer at a time.
Used machines often bring with them issues like password-protected installations. Unfortunately, that's not the only thing that they might bring.
I purchased a used machine from a neighbor who had bought it from his workplace. He is no longer in the neighborhood, so I can't ask him about this. The program, Trend Micro, is the virus-scan program that was on the machine when I bought it. I'd prefer to use AVG but when I try to install AVG, it tells me that there's a conflict with another virus scanner and that I must delete that one before installing AVG. So, I went to Add/Remove programs and clicked on 'Remove'. It came up with a dialog box, requesting that I enter a password in order to uninstall the program. And that's where the problem lies. I don't have the password nor do I know how to get in touch with the guy who sold the machine to me. How in the world can I get rid of Trend Micro? I don't know if it's actually scanning my machine, if it's up to date, or how to use it. Any suggestions?
I do have a suggestion and I can tell you right now that you're not going to like it.
And because I know that there's a really good chance that you won't want to follow my suggestion, I'll throw out a few other ideas as well.
This isn't about removing Trend Micro - they're reputable folk with a reasonable product.
This is about your safety.
This is about what else is on the machine.
The problem is that when you get a second-hand computer, you don't know what else is on the machine.
For all you know, it's infested with malware (perhaps the Trend Micro's a fake).
For all you know, there's illegal content hidden in unexplored corners of the machine.
For all you know, your neighbor was a corporate or government spy and hidden on the machine are our nation's nuclear launch codes or the data to build some kind of bio-weapon.
OK, that last one might be a tad far-fetched in the details (I watch too many movies), but the fact is that you don't know what your former neighbor was keeping on his machine, or just how internet-savvy and safety-conscious he was.
To mangle Forrest Gump a little, a second-hand computer is like a box of chocolates: you never know what you're gonna get.
There's only one way to know what you have: erase the hard disk(s) completely (I recommend DBAN) and install the operating system and all applications from scratch.
I told you that you won't like it, but it's the only safe way to be sure.
As I said earlier, Trend Micro is a reasonable product and I'd even consider suggesting that you leave it on the machine.
If you had the password, that is.
So, the only option is to try to remove it.
As you've seen, the uninstall process is password-protected. That's actually not an unreasonable security measure, but it definitely gets in the way of your very legitimate needs.
Here's what I would try in the order that I would try it:
Revo Uninstaller. The first thing that it does is it attempts to run the uninstall that you've already attempted, but after that, it performs some more aggressive scans of your system and registry to try and remove leftovers. Because everything will be left over, it may have some success. It also wouldn't surprise me if you needed to try it more than once, with reboots in between.
In the Program Files folder (or Program Files (x86) folder), delete the Trend Micro folder or at least as much of its contents as you can. (If you're running Windows Vista or Windows 7, you'll need to do this by running as Administrator, not just logged in as an administrator.) I expect that many of the files will be in use, but perhaps on the next reboot, enough of these will be gone so as to cause a program failure and you can repeat this step. It may also be helpful to first right-click on My Computer, click on Manage, expand Services and Applications, click on Services and look for services related to Trend Micro. Then, you can right-click and stop any of them that you find.
Reboot using a Linux live CD (Ubuntu in the "try it out" mode will do) and delete the Trend Micro Program Files folder on your hard disk. This should work. You may need to clean up some auto-start settings after you reboot back into Windows. Perhaps Revo can clean this up and more for you.
As you can see, it gets kind of ugly. But it should be possible. (You might also check the comments below for additional reader suggestions - I may have overlooked some alternatives.)
And then, yes, as soon as this is gone, make sure that you scan the heck out of that machine with AVG, with anti-spyware tools, MalwareBytes and whatever else that you might want to use to raise your level of confidence that the machine is safe.
As you might guess, my level of confidence remains low.