I don't know anything at all about it. Most of those programs will scan you system and tell you that you need something and you have to pay to get it. I stay away from those programs.
Do you know what file you have missing? Dial-A-Fix might work. Also if you know what file or files you are missing, you can usually find them on the net.
Also have you tried the System File Checker? SFC is a good utility to run when you suspect that system files have been somehow corrupted. It validates the digital signatures of all of the Windows system files and restores any that it finds are incorrect. It will use the on-disk cache if possible, but SFC may require that you provide your original installation CD or a location with an image thereof.
To run the system file checker press Start, Run, and then type in SFC followed by its options.
The most common usage of SFC is this:
SFC /scannow
If you want to use other options , press Start, Run, and then type in cmd. Once the window opens, type sfc /help to see a list of the options you can use.