Hello, I've just formated my system and re-installed XP 32bit using AHCI mode, following the directions on this excellent guide. Thank you Fernando, I could never have figured this out without your guide. The install went fine, and everything seems to work, except I have one strange problem. When a program is doing anything disk intensive, the system seems to block all the other programs very badly. This did not happen when I ran this system with XP under IDE mode (exact same hardware). For example, if I run the benchmark program HD Tune, it runs fine (without any spikes or stutter) but when I also try to use the system at the same time, for example, hover my mouse over "All Programs" in the start menu, it blocks for almost 10 to 15 seconds. Or, if I do a "Save As" in notepad (while HD Tune runs in the background), notepad stops responding for 15 to 20 seconds as if it had crashed, before finally opening the Save As dialog. It's not just HD Tach - if I use the command line program "md5sum" to make an MD5 of a very large (10GB) file, the same thing happens, all other programs are extremely unresponsive and impossible to use. Was I supposed to install more Intel disk drivers after XP installed? I see, in Device Manager, "IDE ATA/PATA controlers" is "Intel® ICH10R SATA AHCI Controler" (126.96.36.1997). (This seems right, since when I built the NLite image, I used drivers "v188.8.131.527 dated 10/02/2009") But, if I look under "Disk Drives", and select my hard drive, under the Driver tab, it says: Microsoft ver 5.1.2535.0 date: 7/1/2001 I know AHCI with NCQ acts differently, but I can't imagine this is normal, it is as if heavy disk use stops multitasking... and as I said, I ran this same system under IDE with no problems. I've installed all the other drivers for my system, no errors or anything out of the ordinary, no errors in the event log... Hardware: drive : WDC WD6400AAKS motherboard: ASUS P5Q-E (ICH10R) Intel E8400, 4GB ram Thanks in advance for any suggestions!!