Here you go:
Boot the 7 dvd , or select Repair my computer from advanced boot menu.
Go to cmd prompt.
( get the drive letter of your 7 partition - it may be different from there - I will use y: , obviously replace y with the correct letter )
cd /d y:\windows\system32
ren magnify.exe oldmagnify.exe
ren cmd.exe magnify.exe
close cmd prompt.
Boot to login screen, click accessibilty icon at bottom left, and select magnifier. Cmd will pop up., type:
net user administrator /active:yes
reboot. At login screen click the new Admin logo and get straight in. Go to System32 and rename those files - scroll down to magnify.exe rt click and rename to cmd.exe, then rename oldmagnify.exe back to magnify.exe
Go to user accounts and clear/change your old admin acct password.
Press ctrl+alt+del and logoff.
Login your old admin acct, open an elevated cmd and type:
net user administrator /active:no