What you would be doing is simply seeing the Vista mbr restored so that version will load up normally on the original drive. That will isolate the second XP drive where you then would either go into the bios setup to change the boot order or the boot device type menu to select the XP drive while leaving the original set as default.
Being new at running more then one version of Windows or another OS the EasyBCD tool makes life a little easier for seeing XP added into the Vista boot loader where you simply select XP when first starting the system from the boot menu screen. There are a few things to know first however in order to see that actually work if you decide later to try a dual boot out rather then enter the bios or device menu each time to load the other.
To see a working dual boot instead of a stand alone for each you still have to first see the Vista mbr restored. Once Vista is back running you download the latest 1.7.2 version of EasyBCD found at
http://neosmart.net/dl.php?id=1
Step #1 following the installation is copying a few boot files over to the root of C on the Vista primary drive. In order to do that you first need to go into any explorer window and proceed to the menu bar>tools>folder options and click to open the view tab seen there. You then uncheck the hidden protected system files option and click apply to see a confirmation prompt.
Step #2 is simply copying the following files now visible at the root of the XP drive over namely the boot.ini, NTDETECT.com, and ntldr files for EasyBCD by itself. An edit of the boot.ini file once unchecking the read only box in the right click properties menu will allow the edit of the copy to overwrite the original when saved not as a txt file but with the "all files" option.
The edit itself would be Step #3 that sees one simply change of rdisk(0)partition(1) to rdisk(1)partition(1). The rdisk(0) is default since XP sees itself on the first drive despite having been installed on the second drive. Y
our mention of being able to boot XP no matter which drive is selected in the boot order suggests the copy and edit are already on the root of the Vista primary but not explaining why XP loads when selecting the second drive. Generally when installing XP after Vista on two separate drives with both plugged in only the root of the Vista host drive sees the boot files placed there and not on the second drive. Did you try unplugging the host drive already for a recovery console repair?
Step #4 is simply seeing using the options in the EasyBCD tool for adding a new entry with a typical but basic gui used there. You place a pin point mark in the add/remove entries selection to proceed to a second screen where the drive is selected as well as the NT/2K/XP dropdown option click the apply button seen there.
