new sata haard drive

[noxiouspb]

I just bought a sata hard drive it is a seagate drive 160gig i bought it becouse it is faster that what they told me at least but it was for the first day or two but now it seems of goten slower i have ran a defrag and a low level defrag i am only useing 18gigs of space it is a sata1 at 150 a sec what ever my mobo is a dfi nf3 250g any way of makeing it faster a should i take it back
btw my old drive was a 80gig ibm deskstar from 2002 and it was faster

[noxiouspb]

ok i just went to services and turned on indexing and setit to auto it seems faster but how do i find out