Studio 1558, display issues

Screen Shows A Mass of Rainbow Colors Then Goes Black But Still Running - Many F12's For A Reboot - Constant Problem.

What kind of problem do I have with my Dell 1558 Laptop?  It's hard to tell?  I am probably way off what I am about to state, but the problem developed after getting on the Dell's website and asking such service to do a maintenance for any possible updates.  Just a normal thing I always did in the past.  Right now I using such computer, but holding my breath it doesn't shut down.  By shutting down I mean the screen goes blank and before it goes blank there is a mass of very small checker colors on the screen.  More of a rainbow display, but fuzzy.  Like I said, this started to develop after the maintenance check by Dell.  But could tell there was a software or something installed.  Have taken the computer back to zero on the hard drive several times and each time after installing all updates from Microsoft looks like the computer is working back to normal.  But after all this updates, say around 200 or so updates no problem at all, and some reason after completing more updates at least 75 to 100 that when the computer screen starts acting up with the rainbow colors and blank screen.  When it does this the computer is still running but with a blank screen.  To get the computer back to a fresh boot with Windows 7 have to do several F12's and sometimes it will take and hour or so to a fresh boot.  In the past with my old XP to format the hard drive this was easy to do,  By now I have no idea how to format the hard drive with my Dell 1558.  I am using the proper DVD program to install a fresh Windows 7, but I don't think it is formatting the complete hard drive.  The computer is 4 years old and I really like it.  However instead of buying a new Dell laptop I bought a ASUS, because I don't trust Dell anymore.  Also, I don't appreciate I can't speak to any tech support in U.S. unless I give them my credit card number.  With ASUS their English is excellent.  Long story, but if anyone know how to do a complete format on the hard drive would really appreciate it very much.  And if anyone knows what the problem is with rainbow colors on the screen would appreciate it very much.  Thanks.