Can you check the following registry key:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Print\Environments\Windows NT x86\Print Processors\winprint
At that registry key, in the right window, is "Driver" of the type REG_SZ and is the "Data" winprint.dll?
Also, check that the winprint.dll exists in the C:\Windows\System32\spool\prtprocs\w32x86 folder.
More info in the following article which is for Windows NT but, in general, should also apply to Windows 7: