I bought a Dell Dimension E520 with a Samsung SP4504C harddrive and VISTA preinstalled. I have a number of programs which will not run in Vista, so I set out to dual boot with XP. Here is my story. NB: This thread has a lot to do with Dell systems and their associated quirks. I purchased Disk Director Suite 10.0 (DD10). Four days later, build 2160 was released. For Vista, this is the one you need. When Vista is preinstalled, OS Selector (OSS) does not play well with the Dell setup. OSS will not detect Vista, but it will detect the Dell Diagnostics Utility partition as having an Unknown Operating System. Any effort to find Vista in OSS was futile. Luckily, deactivating OSS and selecting the Unknown Operating System will boot back to Vista. I decided that formatting both Dell partitions might be fun, and doing so didn't affect Vista in any way. Upon loading OSS in Vista, I found three new unknown operating systems, neither of which was Vista. But, I activated OSS anyway. Big mistake. This time, deactivating OSS just left a blank system. So, in a fit of rage, I formatted everything using the DD10 bootable disk. Three pieces of advice at this point: 1. Install DD10 and create the bootable disk, 2. Backup everything! Grab a DVD or two or ten and backup everything dear to you, 3. Download all relevant Dell drivers for XP from support.dell.com and burn them to disk. Be sure to include the Network Adapter Driver. One other point: Delete all the old Dell partitions and create new ones as desired. I made two primary NTFS partitions for XP and VISTA (30 GB and 40 GB, respectively) and a logical NTFS partition for data. To do this, use the Acronis bootable disk (ABD) by hitting F12 at startup, and enter DD10 Safe Mode. I then tried to install XP, but kept getting a blue screen error reading "STOP: 0x0000007B". Dell support directed me to the BIOS setup (F2). Under SATA Operation, select RAID Autodetect/ATA. XP will install after this. However, being stubborn, I installed Vista first. I couldn't get the dual boot to work this way, but it may work. I reformatted everything and started with XP. I installed DD10 and placed OSS on the logical drive. Restarting to OSS will show XP. However, a Windows CD/DVD will not be detected by OSS. (My guess is the program doesn't have the right drivers for the DVD-ROM.) I booted to ABD and entered the DD10 safe mode. In there, I hid the XP partition and set the Vista partition to active. Commit the actions before exiting. Exiting before committing causes the program to freeze. Then I booted to the Vista Reinstallation DVD. One of the install screens allows you to select the partition. I let the DVD format the Vista partition before proceeding. When Vista finished installing, I booted to ABD and repaired OSS. Then, I entered DD10 Safe Mode and found that the XP partition had been deleted. I used the Recover tool, using the Manual setting and Complete scan. That repaired the XP partition. I then ensured that all partitions were unhidden and made the XP partition active. I shut down and returned to OSS. Vista would not load. This may not happen to you. If it does, delete the Vista icon in OSS and use the OS Detection Wizard to find the OS in the Vista partition. (While you're in the wizard, be sure to set the XP partition to hidden. It will save you a step later.) Then, check to make sure that the proper partitions are hidden for each of the operating systems. To do this, click the properties menu for an OS. Under Partitions, select hidden for the unwanted partition and under Advanced click force hiding partitions.