I have exactly the same problem.
I just bought 6Y120P0 120 GB, 80 GB platter version, and it seems much slower, than the reviews shows.
The performance is about 49/22 (41 Mb average) with some quick tests with AIDA, however HDtach shows 54/11 (36.5 Mb average).
Measured on Abit NF7-S v2.0, latest bios (Nvidia Nforce2, Windows XP+SP1, Athlon 1700+)
Is the performance/quality of this model so poor or my drive is faulty?
Could someone try a test with AIDA disk benchmark (in menu open Plugin/Disk benchmark)?
AIDA sysinfo tool
You can download it here: AIDA Personal (freeware)
I would be curious what results others get.