Welcome to
D-A-L,
Please, if you have no backup of your system read my backup suggestions at the bottom of this post.
If you have no backup of your registry, please download and install
Erunt reading thoroughly the section relevant to Windows 7 and Vista OS.
Automatically backup your Windows Vista Registry daily with Erunt
This
link from Microsoft may also be of interest to your issue, but again read through it fully to evaluate it before changing any settings.
If you are unsure of anything or want further assistance, don't hesitate to post back with questions.
best regards,