If i understand... your XP get blocked when trying to generate the list of installed software that can be removed, right?
Well, maybe you ahev a slow machine and maybe a lot of software installed. This is just a problem of getting bussy the application doing something that freezes it because its a lot of work for the speed of your computer.
Try to shut down your PC, wait a few seconds, start it, shut down all the software running (even the ones that are beside the clock), dont open office or that kind of heavy software... then try to use the same panel.
If this DOSENT works, the try to check what software are running at start up (see the registry or if you dont know how to do it, use some software to do it) and get out everything that its not really needed.
The last possibility is that maybe you have some spyware or virus that are using all your CPU and making your PC so slow.
Did you feel slow your machine?