Open the command line - press Win-R, type CMD and press Enter
Type the following command:
wmic qfe [Enter]
You'll see a list of updates that are installed on the computer. They have KB reference numbers, these refer to the Microsoft Knowledge Base articles they are fixing.
To put this list into a file so you can easily e-mail it, use this command:
wmic qfe > kb.txt [Enter]
A file called kb.txt will be created in the current folder. The prompt shows you which folder this is, typically C:\Users\username\. You can open this file with Notepad or e-mail it.
There's an alternative command you can use:
It's really nice because it gives you lots of details about your computer.
WARNING! If you are sharing these details with others be careful, potentially some information could be used by hackers to attack your computer.
Again if you want this data in a file just add the greater than sign and a filename:
systeminfo > systeminfo.txt [Enter]
Look at C:\Windows\WindowsUpdate.log, this file contains a list of installed updates.
I hope this little tip has been helpful :-)