I need help

Hey all you Facepunchvillians i need some help with my gmod 10 aka Garrys mod

so when i was playing i thought hmm so i went to the options and put it in run in windowed mode and as soon as i pressed accept Poof it crashed and i havent been able to fix it ive tryed deleting the config file the client registery blob and defraging and doing the vefify the cache thing so please can someone help

yours Sincerely CABBSA BTW i know the bad spelling

Whats the crash really? Steam error? Memory error? Other error?
Post your system specs, Oh and clean your gmod

In GMOD Launch Options, type -fullscreen