Try to System Restore to a date/time prior to when the problem began. Start > Programs > Accessories > System tools > click on System Restore > follow the prompts.
A non-destructive System Recovery. Go to Start > Programs > System recovery > Click on System recovery > follow the prompts. This may require re-downloading/installing MS Updates.
Another option may be sfc /scannow. Go to Start > Programs > Accessories > Command Prompt. Type "sfc /scannow" w/o the quotes and press Enter. Note that there is a space between "sfc" and "/scannow". This can take a half hour or longer, so be patient.
Hope this is helpful.
When I go to the search feature on Windows XP, a box opens but its contents are completely empty...it is a big white box; same happens when I go into the control menu and try to access user accounts -- a box pops up but it is empty...nothing can be accessed, it's completely white...sometimes when I am using a program on internet explorer, such as lexus nexis, i cannot log in because a log in box pops up, but it is empty....i am baffled...is it a control feature?