My computer boots up but then all i get is the egg timer

FIRST OF ALL REMOVE ALL THE EXTERNAL DEVISES LIKE PEN DRIVES OR PORTABLE DRIVES.
just restart ur comp n press F8 key continually it will opean a dos type window n choose start windows with SAFE mode through the help of ur up n down keys. It will open ur OS whatever is it with customize use u not hear sound, not able to connect internet n so n so... just remove ur temp file , cookies, prefetch files, through run
open run prompt : temp file type %temp% n deleate all files cookies file type cookies " prefetch file type prefetch "
* delete all containing file n folders if some files r not deleting just skip them
after this process open run command n type msconfig it will open system configuration utility choose general n click on ( normal startup- load all device drivers and services) after that click on startup n click on Disable all then aplly n close it will ask u for restarting ur computer click on Restart n wait until ur system not getting restarted.
IF UR COMPUTER IS NOT TURNING ON SAFE MODE OR IT'S SHOWS BLUE SCREEN AFTER TURNING ON THROUGH SAFE MODE , RESTARTING AFTER SAFE MODE THAT'S MEANS BUDDY UR WINDOWS HAS BEEN CLASHED N U HAVE TO RE INSTALL IT.