To restore the option for XP:
1. Check My Computer to see if your XP partition is visible. If you can't see your XP partition, you need to assign a drive letter to your hidden XP partition. To do that, open Control Panel - Administrative Tools - Computer Management - Disk Management. Right click on the partition without a drive letter and select "Change drive letters and ...." and assign a drive letter , e.g.
D:. If you already can see the XP partition , skip this step, just note its drive letter.
2. Open an elevated command prompt (run as administrator) and type:
Code:
bcdedit /create {ntldr} /d "Windows XP"
bcdedit /set {ntldr} device partition=D:
bcdedit /set {ntldr} path \ntldr
bcdedit /displayorder {ntldr} /addlast Note: Change D: above with the letter of your XP partition
Reboot, and you should see Windows 7 and Windows XP as startup options.