I'm looking to find out if a KB is installed via command line.
PowerShell 2.0 contains the get-hotfix cmdlet, which is an easy way to check if a given hotfix is installed on the local computer or a remote computer. An example of the basic syntax is
get-hotfix -id KB974332
run "systeminfo" in a CMD window and it will pull back a load of statistics about your system including what patches are installed.
Some other possibilities: Grep %windir%\Windowsupdate.log for the KB number. Or use reg.exe to export the corresponding install keys.
wmic qfe list /format:htable>C:\PatchList%Computername%.html
Above command will give the output in html format.
As someone asked about using wmic at a PowerShell prompt, just use Select-String (or sls).
wmic qfe get hotfixid | sls "KB99999"