I recently tried installing backtrack 2 to my hard disk and I realized that I made a mistake specifying where to write the MBR to. I have windows xp on my primary HDD, and an external USB HDD that I just partitioned recently to install ubuntu and backtrack on. Now, I wrongly specified in the backtrack installer to write my MBR to /dev/sdb, which is my external HDD, although after searching online I realized I should have made it /dev/sda. Now, how do I uninstall backtrack to reinstall it again, or get the MBR on my primary. I tried deleting all the folders in the partition that I have backtrack in (sdb3), which I guess is a pretty newbie thing to do cos it didn't seem to delete it... How do I correct this problem? I've tried searching this forum and elsewhere, and they say that I could use the windows xp recovery fixmbr, but can I just reinstall backtrack in the partition sdb3 and write the MBR to the internal HDD?

What's happening now, is that when I load, I get the following message -

Grub loading stage 1.5
Grub loading please wait.....
error 21

However, when I hit Ctrl + Alt + Del, I can see my Windows XP and Ubuntu booting options. How do I just delete the data on the backtrack partition for a full reinstall? Will the backtrack installer give me this option? Do I have to remove the MBR from the sdb before writing to sda?