(This is obviously just some random person's opinion, and not advice from any major software company.)
Logoff/Logon, instead of rebooting
Windows occasionally gets into a weird state where, well, things just stop working - the start menu doesn't launch some apps anymore, clicking links in Internet Explorer doesn't work, context menus stop working, etc.*
Instead of rebooting Windows to get things working again, try logging out and logging back in. When Windows (and the apps that plug into the Windows shell) get into some weird state, you don't need to reboot; a logoff shuts down the Windows Explorer, and a logon loads it again.
The system services in Windows generally don't get into too weird a state. So they can just keep on running during your logoff/logon.
Recreate your profile instead of reinstalling Windows
On your home machine (not a domain-joined machine):
If your Windows installation is in a terrible state (too many application installs and uninstalls, weird application crashes at weird times, file associations that don't work anymore, etc):
Instead of wiping and re-installing Windows**:
Back up all your files
Log on as a different user on the machine
Delete the user profile of your user (in Computer Properties, Advanced Settings)
Log on as your old user account
All your files will be gone (you did back them up, didn't you?) but you will have a clean registry, and as far as all applications are concerned, you are a new user.
Restore your files
The Windows registry consists (simplifying here) of two parts: HKLM (machine settings) and HKCU (your user settings)
When Windows gets into a weird state, you can mostly fix all the issues by deleting HKCU (by deleting the user profile), instead of reformatting the disk (which, obviously, gets rid of HKLM and HKCU)
You lose some settings in some apps (because you start off with a fresh HKCU) but you were going to reformat and reinstall anyway. And you don't need to reinstall all your drivers. Again.
(Translation for Unix types: This method is about the same as deleting all the .* files in ~, I guess.)
*My Macbook gets into the same state sometimes (I get unejectable CDs, for some reason). The same logoff-logon approach works there too.
**Don't do this if you rely on certificates in your user cert store, for things like EFS. This method makes bad things happen in that scenario, I think.
And some applications (some games) don't like this method. But things like Office just keep on working.