I installed openSuse 10.3 from a USB pendrive following the steps stated at SuSE install from USB drive - openSUSE
The installation completed just fine. But I can now boot only from the USB drive only and not my internal HDD. Is there a way to fix this without the need to re-install openSuse?
You need to re-install grub to the computer HD.
read this carefully
GRUB Boot Multiboot openSUSE Windows (2000, XP, Vista) using the Grub bootloader.
Also, please describe which operating systems are on the internal HDD so we can maybe suggest some options.
This thread might (or might not) be relevant depending on your mix of operating systems:
windows main dirve and opensuse on usb harddisk - openSUSE Forums