My PC keeps blocking

Please provide all your PC specs including brand/model speed. watts etc..

What is the PC blocking? Can you boot to desktop? What messages are on the screen? If you have the cd disk, you may need to do a "Repair".

If you get a message that no operating system is found then you may have to change the primary boot device back to the hdd, in the bios. I had a similar issue with a Dell PC and an Acer, it's some sort of security feature.