1. Click on the 'Start' menu and type 'cmd' in the 'Search' prompt. When cmd comes up in the results, right click on it and scroll down to 'Run as administrator.' Type in any necessary password and click 'Continue.' If cmd opens, skip to step 5. If you do not have a 'Start' menu available, move on to step 2.
2. Boot from your Windows Bootup CD or DVD by inserting your CD or DVD, starting your computer, hitting F2 (or Del) as the computer boots up to bring up the BIOS, and selecting your CD/DVD player as your Boot Device Priority instead of your hard drive. Exit the BIOS to start your computer boot up.

3. Click 'Next,' then 'Repair Your Computer,' choose your Operating System from the list, click 'Next,' and then click 'Command prompt.'
4. Type 'SFC.EXE /scannow /offbootdir=c:\ /offwindir=c:\windows' and hit 'Enter.' Let the process run. Once it is complete, restart the computer, go back into BIOS, restore the hard drive to the top Device Priority position and try to start up Windows. If it starts up but Explorer is still causing trouble, go to Step 5.
5. Insert your Windows Installation CD. Type 'sfc /scannow' in the command prompt and hit 'Enter.' This will check your Windows protected files like 'Explorer.exe' and repair them using the Windows Installation CD. Restart your computer and all of your programs should be functioning properly.