My Energy Management turns off the PC screen every few minutes, even if I'm playing something with VLC Portable. I remember that the 'normal' VLC didn't have this 'problem'.
Is there an option to suspend Energy Management while playing? Where is it?
PS: No, changing Energy Management settings is not a viable course of action
PPS: Sorry for my english, I'm italian.
Caffeine is a small freeware (though not OOS) application which will do what you want. I have run caffeine off my usb drive - not sure if it truly portable.
From the website http://www.zhornsoftware.co.uk/caffeine/index.html
Caffeine
If you have problems with your PC locking or going to sleep, caffeine will keep it awake. It works by simulating a keypress once every 59 seconds, so your machine thinks you're still working at the keyboard, so won't lock the screen or activate the screensaver.
The icon is shown above - it's the leftmost one in the task tray, and this is all you see. Double-clicking the icon empties the coffee pot (that's what the icon is) and temporarily disables the program. Double-clicking it again refills the pot, and will keep your machine awake.
Windows 98: Caffeine works by simulating left shift key down and up events every 59 seconds.
Windows 2000/XP: Caffeine works by simulating a left shift key up event every 59 seconds.
Of all the key presses available, shift is probably the least intrusive, and least likely to interfere with your work.