There are many patches....
Run Windows Update to determine what you need. If you have never run the
update routine, then you may be lucky to have some of them consolidated into
the larger Service Pack 1a. But there will still be others to install.
Sometimes you'll need to reboot after an installation. Sometimes not. It
depends on the specifics of the patch. Do not try installing every last one
of them at once....
The icon for the Windows Update tool should be on your Start menu, but if
yours is not configured that way, then....
Windows Update can be found on your PC by clicking:
START, then "Help and Support", on the right, under "Pick a Task" should be
"Keep your computer up-to-date with Windows Update". Click that link, and
follow the prompts.
Also, one final note: you can configure the computer to automatically check
for updates, if you wish. You can choose whether you just want it to look
for them, look for and download them, or look for and automatically install
them....
Click START, then "Control Panel", then "Performance and Maintenance", then
"System", then "Automatic Updates" tab, to change these settings.
Good luck,
-Lawrence in Seattle