A friend of mine had a computer go down and needed the info off the hard drive so he tried installing it as a slave in another computer. That would not take so he installed it as the master and the other one as the slave and it worked. He got all the info off that he needed but now when he went to put his back in as a master it says something like can't load explorer.exe. You must reinstall windows. Why would this happen?

Did he directly copy over everything including the Windows directory? If so, he would have messed up his install. He'll have to do a repair install of the operating system to fix it.

For future reference, his computer most likely didn't load when he added the other drive because he didn't set the master/slave jumper settings on the drives correctly.

No, all he copied was address book, pictures and I think some emails and documents.

check the system.ini file (C:\Windows\system.ini). Scroll till you find a line that starts with 'Shell='. Make sure it reads as 'Shell=explorer.exe'. Save the file and reboot. You'll need to do this from a DOS window (obviously). Once you get to a DOS Prompt, type the following commands.

C: <enter>
cd \ <enter>
cd windows <enter>
cd command <enter>
edit C:\Windows\System.ini <enter>


Change the line to read as shell=explorer.exe
Save the file and restart the computer. If this doesn't help, post back here.

it is long time i seen this problem with many users.
Most likley user profile is corrupt. After through task manager running explorer.exe,if u can create user or login as adminstartor and and copy from admin desktop to user desktop.
logout and login with administrator again and restart computer and login as user this time. it will work.
thanks,
Raydar