You need to reinstall the boot manager. NTLDR can't boot Windows 7. Start the Windows 7 install DVD, and choose "Repair" and "Command Prompt". At the prompt, do a "bootrec /RebuildBCD" to write down a new bootloader. I can't promise that this is going to keep Windows XP in the boot order, but it will restore the ability to boot Windows 7. After that, you can follow any number of articles to get Windows XP back into the boot manager manifest. ======================================================== Once installation of XP is successful you can now install the latest Microsoft Updates and drivers. You will undoubtedly notice that the machine is booting directly into XP at this time. This is due to XP writing its bootloader over Windows 7’s. To get both XP and Windows 7 as an option at the boot screen you can use the free utility EasyBCD 1.72 or their new 2.0 Beta. VistaBootPRO 3.3 (free version) will still work too which you can download here. VistaBootPRO is now called DualBootPRO and is no longer free, it’s $9.95 for a single user license. After getting the bootloader back you should see both XP and Windows 7 as options in the Windows Boot Manager. ========================================================== My situation was Windows 7 on C: partition, Windows XP on D: partition and with the PC booting into XP automatically. First step, get Windows 7 to boot. Run the Windows 7 DVD and repair an existing installation from the command prompt. bcdboot c:\windows /s d: The "d:" specifies the target partition where boot files are copied. My first try was with the target partition "c:" but this didn't work as "d:" was the current boot partition. This got Windows 7 booting OK, but then I needed to add XP back into the boot options. From a command prompt (run as administrator) in Windows 7... bcdedit /create {ntldr} /d "Windows XP" bcdedit /set {ntldr} device partition=D: bcdedit /set {ntldr} path \ntldr bcdedit /displayorder {ntldr} /addlast XP was was now showing in my list of boot entries. The final step was to copy the boot files "ntdetect.com" and "ntldr" into the D:\ root directory.