c:\windows>attrib -s -h -r system.dat enter
to check if you have done this right at the prompt
c:\windows>dir system*.* enter
you should see a file called system.dat.
If yes then continue if you can not see system.dat then you may have missed a space.
If the system.dat file does show up.
c:\windows>ren system.dat system.bad enter
Reboot the computer does it now start windows?