I think I'm totally misunderstood here --

I DO NOT have Linux installed on USB drive. As mentioned in the first post itself:

Here is my config, sda and sdb both are SATA drives. Windows XP is installed on sda and Linux on sdb

sdb has the following partitions:
sda1 -- NTFS ~920GB
sdb2 -- linux-swap 4 GB
sdb3 -- fat32 6 GB
sdb4 -- ext4 70GB