Are you experiencing a lot of problems now that you have been using your computer for a while? It seems the more you use your computer the more problems you have. Do you know what this is? It is because cleaning the registry is apart of general maintenance of your computer. You should clean your registry once a week before all the problems build up. It is like cutting the grass, you want to cut it enough so the grass doesn't get to long for your lawn mower to handle. What this means is once all these problems build up it may be to much for your computer to handle resulting in windows xp crashing and freezing.
If you don't let these problems build up then you shouldn't have to many problems down the road. Basically if you use your computer a lot, run a scan once a week to insure to yourself that you don't have any problems with the registry. Once it is done then you are basically done for a week and don't have to worry about xp freezing or crashing.