A repair usually works fine but it can go a bit wrong at times. What data are you unable to access? As for the apps they should work fine. You could uninstall those apps not working and reinstall them. Make sure to do a good reg clean after uninstalling apps.
Have you thought of saving any work to disc then wipe your drive and do a fresh clean install.
Once that is done and you have your XP running smooth once again with all software reinstalled you should then make an image (i use Acronis myself) and save the image to either a DVD disc or partitioned drive or slave drive if you have one. Once this is done no matter how bad your PC gets in the future it will take you no more than 10 minutes maximum to reinstall your image and your Computer will be back to perfect running order.
Here is what i do. I wipe my drive clean install XP then install all software i use get all updates installed then once this is done i then make an image save the image to my slave drive now say after a few months and my XP is running slow or a problem occurs i cannot fix all i do is install my backed image within 10 minutes and my computer is as fresh as the day i installed XP.
