From time to time you'll get an environment where the Windows boxes are so locked down that it's a huge pain to try to play with the settings to avoid the screensaver locking the screen, etc. Also, there may be some cases where you just need to temporarily get around a screensaver/power settings for a Powerpoint or something. Maybe you are on somebody else's network and don't want them to get miffed about configuration changes being made. Or maybe you have a gray hat use in which case you are a loser.
Well, these all sound like a case for getting the awesome free lightweight application Caffeine to make your life easy. Simply download and unzip the executable and run the completely portable app from your hard drive, thumb drive, network drive or cloud drive -- no admin privileges required and no install necessary! If you give onsite presentations to your customers in their conference rooms, etc. and are sick of annoying screensavers, then give it a whirl!
Basically, when you run the executable it places an icon in your taskbar and immediately starts its screensaver-toasting wonders. You can use the taskbar icon to disable it temporarily or exit. If you want to get fancy, you can use the command line switches. The beauty of it is that this is simply a standalone executable that emulates a F15 key up event every 59 seconds.
Don't forget, this app has some pretty serious security ramifications, so use with care. There are huge benefits to computers' screensavers locking the screen to require a password when inactive. If you step away for coffee and the janitor snoops on your email, you may be kicking yourself in the back of the head with great force. Consider only using this application as a temporary measure for special cases and if you are going to be within view of your computer. Don't be stupid. Don't hack yourself.
I've tested this on XP Pro 32 bit and 7 Pro 32 bit and it appears to work even without admin privileges. The maker's website also has other freeware-awesomeness apps so check them out, for sure!
In addition to the hotlink above, you can download Caffeine from my online storage here. Enjoy the Caffeine high!
UPDATE: Mac users, you can run the command "caffeinate" from the Terminal to achieve the same thing! (Run "man caffeinate" to see options.) Or, download Caffeine from the App Store!