"Someone told me that reducing my browser cache will help increase battery life as the cache is forced into ram and not on my hard drive. Is this true and how do I do this in IE?"

Odd, but I guess it could go either way.

"Also I was wondering if I set CPU priority to low when doing ctrl alt delete on windows media player, will this increase battery time while watching movies? thanks!"

Try "MEDIA PLAYER CLASSIC" and "WINAMP" since these are lighter weight applications.