mee987 - Yes I have HDtached my D740X 40gig and 80 gig drives.
I use the 80gig as a backup drive, It's set as Primary Slave. It shows great HD tach socres, 11.8ms access, 35,000kbps read, 5.5% CPU utilization, no wierd spikes.
I got the 40 gig drive to use as my boot drive. I set it as Primary Master and installed my OS and apps. Ran HDtach and got real weird results. Access was good at 12.2ms, read was real flakey: started off at only around 25,000kbps until it got to around the 22Gb area where it then went UP to 35,000+, but during all this there were these incredible spikes that went down to as low as 800kbps. The average read speed came out to onlty about 25.000kbps, CPU was 10%. Of course DMA was activated etc. Tried reformatting, no change. Installed Win2000 (instead of XP), no change, tried Win98, no change. Ran the Maxtor diagnostics (from the floppy - "MaxDiag" - I think) and the drive passed all the tests with flying colors. Then I wiped the drive again and set ist as a slave, installed it in my system and ran HDtach again. It came out great, 12.0ms access, 34,400kbps read, 5.4% CPU, no spikes. Go figure...... I couldn't so I RMA'd it back to Newegg. The drive seemed to work fine but that HDtach stuff really bugged me.
For now I'm sticking with my tried-and-true (knock wood) 60GXP's as my boot drives. I suppose I'll try the Maxtors again one of these days.
BTW - I don't know if it matters but the 80gig drive is a "j" ball bearing drive and the 40gigger was a"L" fluid bearing drive.