Windows 7 Evaluation HDD Issue

Am currently trying windows 7. due the performance increase after ive done all my usual performance tweak.

My question is that even after i did all of this. i seem to still be getting the same issue.
My secondary Drive which is a Western Digital 160gb 7200r.
Seems to spin down after a certain amount of time. usually when i run a demanding program. i.e GTAIV or Photoshop CS. is this normal. i cant seem to find any info on this subject. i understand as win 7 is not even out yet. but its basicly a revamped vista. right. ?

Its not bothering me too much. its just i have all my music backed onto it. and when i start winamp or what not. it starts as some of the tune is buffed in my ram from when i had it playing earlier. as i often use winamp, then its stops, i hear the HDD spin up, then the music continues from where it stopped at.

will this reduce life expectancy for this drive or is this a good thing for it to do. also i see in another forum post, saying that its not spinning down its the head moving off the platter. for safety reasons. so its not sat on the disc/platter all the time. i think i got that right.

Sry for long post. not good at asking questions, just ansewring them :)