Ok I have been pulling my hair out with this problem for a while now but hoping someone will have a solution for it. The spec for my pc are listed below. Ok here's my setup SATA1 is connected to a hard drive with two partitions (FAT32 and EXT3 for Linux). FAT32 is the primary (boot) partition with the boot manager SATA2 is connected to WINXP hard drive SATA3 is connected to VISTA hard drive SATA4 is connected to a hard drive used for gaming SATA5 AND SATA6 is setup as Raid 0 for video editing BIOS boot order is set as Floppy, CD ROM, and Hard disk Hard drive order is set as SATA1, SATA2, SATA3, SATA4, RAID-0 Without the raid drive conected, I can boot any of 3 the operating systems with no problem whatsoever. With the raid drive connected, XP will not boot comes back with "\system32\hal.dll missing" error message. Meanwhile I have no problem booting Vista or Linux with the raid drive connected. Another crazy thing about this is if XP installation CD is in the cd rom drive during bootup and I ignore the "press any key to boot from cd" message, then I am able to boot XP! Without the bootable cd XP will not boot. After doing much googling and troubleshooting, I narrowed it down to winxp bootloaders (ntldr and netdetect.com and boot.ini). With raid drive connected, it appears the bootloaders are looking for XP in the 3rd hard drive (Vista location) instead of the 2nd hard drive. How did I know? Well I boot into Vista and modified the boot.ini file as follows: original--> multi(0)disk(0)rdisk(1)partition(1)\Windows="Microsoft Windows XP" /...etc modified--> multi(0)disk(0)ridisk(2)partition(1)\Windows="Microsoft Windows XP" /...etc With the modification as shown above, XP boots without having to use bootable cd. This does not make any sense since BIOS disk order remains the same Now after modifying the boot.ini, if I use bootable cd, XP will no longer boot since it will actually try to boot XP from the 3rd drive based on the modification of boot.ini So my question is how come the bootable cd is able to follow the BIOS disk order but XP bootloaders are not? Is this a nvidia raid controller driver issue since the problem occurs only when the raid drive is connected. Does anybody have an idea why this is happening?