Comp Constantly Reboots

[TooleJoshua]

After the power is turned on it starts constantly rebooting itself never shows any words or anything just a constant black screen as it keeps rebooting how can i get into the command screen or boot in safe mode when it does this id like to keep the files on it but if necessary i can manage without the files?

 

[CAMusing]

Using the operating system CD to boot then do a repair install.