Here is a response from blitware.
I am truly very sorry for any and all heartache and inconvenience you may have experienced using PC Medkit. Recently a small patch was released for PC Medkit that should not have changed any functionality at all but unfortunately has caused a small percentage of our users to experience some massive software failures. You'll know if you're experiencing this issue if you've restarted your computer after running PC Medkit and you can no longer boot into Windows.
We've come up with some simple steps you can take yourself that we hope will get you and your computer back up and running as before. We've also sent through a full refund for all your purchases including PC Medkit which will be credited to you within 5 business days when the transaction goes through.
PC Medkit does take advantage of the Windows System Restore function and creates a restore point each time it is run before making changes to the system registry. Unfortunately the error caused by PC Medkit is preventing many computers from logging into Windows Safe mode as well which makes it much more difficult to repair using this function.
Depending on the operating system that you are using the System Restore function can be accessed from the Windows install CD. If you are running Windows Vista or Windows 7 please review the link below on how to access System Restore via the Windows disc. If you follow along with this guide you should have your system back to normal in just a few minutes: Using System Restore from the Vista Windows Recovery Environment
If you are using Windows XP unfortunately the problem is a little more severe as the XP install CDs do not have the same recovery functions as Vista and Windows 7 do. It is likely that you will need to format your hard drive and reinstall your operating system from scratch. If you have any important data saved to your main hard drive you may want to bring your computer in to a service tech and have them attempt to recover it before reinstalling your operating system. In this case please let us know right away and we'll get back to you with important information.
To see the full history of the conversation between you and your Blitware support worker, or to reply to their message, please visit the following link: Get support for your Blitware products!
Thanks again for letting us help you!