This seems to be a very common issue on Windows 7 caused by a recent "Important " update.
I'm still trying to determine which update was provided by Windows Update that causes the issue but the problem goes something like this:
Check in %windir%\system32 (C:\Windows\System32) for the existence of spoolsv.exe.org and spoolsv.exe
If they both exist then it is likely the following issue.
Compare the file sizes:
Sometimes the real spoolsv.exe will be named spoolsv.exe.org [545KB] and in the place of spoolsv.exe place will actually be a 41KB file posing as the print spooler.
Rename spoolsv.exe to spoolsv.bak
spoolsv.exe.org is a little more tricky as it requires changing the file ownership from TrustedInstaller to the Administrator Group and giving the group full write permissions for the file. This likely has security implications so it's recommended to revert the permissions after the file is renamed.
By changing the Ownership of the file from TrustedInstaller to Administrator then enabling Full Modify for the Administrator Group you can swap the files over and correct this issue and then start the print spooler via services.msc or net start spooler.
I usually rename spoolsv.exe to spoolsv.bak and then rename spoolsv.exe.org to spoolsv.exe.