New parts are not working as well as they should be. help

ok, so i just recently built my first computer, my parts are listed below.

I7-920 processor (not overclocked yet, using stock hsf)
Asus P6T Motherboard
XFX GTS 250 512mb
Raidmax Smilodon Case
Seagate barracuda 7200.12 1tb
600w OCZ power supply
corsair xms3 1600 3x1 gb

the computer worked first time i booted, and when i checked the bios hardware monitor, the cpu temp was at 40s-50s, which isnt a normal idle temp. i kept going and installed my os, xp 32-bit, and installed drivers. then, the cpu temp worried me, so i removed the heatsink thermal paste, and applied an old arctic silver 5 onto it and remounted. when i booted, the cpu temp was the same, 40s-50s. i read somewhere that the arctic silver 5 takes 200 hours of operation to break in, so i left it and decided to keep it for a week or so. next, i installed 3d mark 06 to see my benchmarks. it ran, but not quite well. my older brothers computer had better benchmarks. he has a q6600 and a geforce 8 series, not sure which. when i arrived at the cpu test, my cpu monitor beeped sounds warning my that my cpu temp was at 80 degrees, so i aborted immediately. i do not know whats going on, whether i just have to use the computer more often so the hardware breaks in, or somethings wrong. suggestions/advice are appreciated.

im pretty sure i mounted the hsf properly, i tried several times and when i try to move it, its solid in place. i put the drop of thermal paste on the hsf' circle, and it fills most of the cirlce, just not the edges.