Windows wont boot

hey guys i fixed my power supply problem (i replaced my 450w max Power Supply with a 300w max one i found lying in my garage)but now whenever i try and boot to windows, the system automatically reboots right at the windows loading screen and i cant log in safe mode either....WTFUX?!

>>2
you're stupid shut up.
First off "Mr. Red box" its 300w
NOT 300V you know nothing!
second you dont have to go into the BIOS for an hour to find out if its the problem. just put the 450w ps back in & if it boots then you know it was the problem.