so if the "available" number is far away from zero (300+ mb), is it safe to set the page file to zero? what confuses me now is that i have unused ram, but the page file is using 550~ mb
If you're only using 302MB right now, I see nothing to worry about. I don't always pay attention to how windows divides up the physical RAM/Page file, but you're certainly not using too much RAM...
cachemanxp is crap and total nonsense. totally useless as far as i'm concerned. My suggestion is to never set your pagefile to 0. I've got 2gb and still got 1.2gb pagefile.