To resolve this problem, modify the Windows XP Boot.ini file to point to the correct partition. To do this, follow these steps:
1. Start Windows Vista.
2. Right-click Start, and then click Explore.
3. On the Organize menu, click Folder and Search Options.
4. In the Folder Options dialog box, click the View tab.
5. In the Advanced settings area, click Show hidden files and folders, click to clear the Hide extensions for known file types check box, click to clear the Hide protected operating system files (Recommended) check box, click Yes to confirm that you want to display operating system files, and then click OK.
6. Locate and then click the Windows XP system drive. In the Windows Vista Windows Explorer program, this will likely be drive D.
7. In the right pane, right-click boot.ini, and then click Properties.
8. In the boot.ini Properties dialog box, click the Security tab, and then click Advanced.
9. Click the Owner tab, and then click Edit.
If you are prompted for an administrator password or confirmation, type your password or click Continue.
10. In the Change owner to list, click your alias or leave the default Administrators option selected, and then click OK four times.
11. Right-click boot.ini, and then click Edit.
12. Modify the Advanced RISC Computing (ARC) path as appropriate for the correct path of the Windows XP startup partition. For example, if the Windows Vista Setup program created a partition in the unallocated disk space in front of the partition on which Windows XP is installed, you must increment the partition value by one. Therefore, if the Boot.ini file contains partition(1) along the ARC path of the Windows XP operating system, modify the ARC path to use partition(2). In this situation, the ARC path resembles the following:
multi(0)disk(0)rdisk(0)partition(2)\WINDOWS="Microsoft Windows XP Professional" /fastdetect
13. Save the changes to the Boot.ini file, and then exit Notepad.