What could it be?

I recently uninstalled ZoneAlarm and it didn't go so smoothly. At one point it, it said it wasn't responding. It then just sort of stopped midway, with no instructions. So I then went to the ZoneAlarm folder, double-clicked the uninstall button and it emptied itself.

As this didn't seem right, I thought the program could of left data still on the computer. So I tried to clean the registry using probably the most recommended program for it, Registry Mechanic (PC Tools). There seemed to be a lot of errors.

At no point did I look at the Add/Remove Programs tool apart from initially trying to uninstall ZoneAlarm, via that way.

I then restarted my PC.

After this, I went to uninstall another program but there's a lot of info missing on the Add/Remove Programs tool. Examples would be, hardly any graphical icons in the list for each program, and the sizes in MB of each program/utility missing. Plus, no info on how frequently each program is used (rarely/frequently) etc - apart from one program.

I know don't know whether it was the crappy uninstall or registry clean that may of caused this problem. Also, System Restore won't restore back to the time I was about to uninstall ZoneAlarm. So, I'm screwed. Any clues people?

Help would be appreciated.