For Win95/98/ME 
With Cabfiles On HD Or Windows CD in CD Drive And Windows Boot Floppy Diskette:

Error Message: Error Loading Explorer.exe You Must Reinstall Windows
When you click OK, you may receive the following error message: 

A required .DLL file, C:\WINDOWS\SYSTEM\MSVCRT.DLL, was not found. 
You may then be unable to start Windows. 

Boot computer with Windows boot floppy
Bios must be set to boot from floppy before Primary hard drive

At command prompt Type ext, press ENTER 
 
At the Please enter the path to the Windows CAB files (a:): prompt, 
type path to Cab files on HD or Windows CD > press ENTER.

Enter the name of the file you want to extract: 
type msvcrt.dll, press ENTER

Enter the path to extract to ('Enter' for current directory): 
type c:\windows\system, press ENTER.

type y, and then press ENTER to extract the file to the specified directory. 
Remove the Windows boot floppy disk, and then restart the computer.

NB
A Windows boot floppy can be dowloaded from http://bootdisk.com