Hello,
You may be able to map the external drive or folder on the drive with a drive letter.
In Windows click Start, Help and Support and search key words "map drive letter".
You can use another backup application as needed. If you have XP Pro Microsoft Backup can be used to backup to a file with the external drive's letter as the destination. Microsoft Backup normally can be found by clicking Start, Programs, Accessories, System Tools and choose (Backup).
I do not understand the third question, however, the information I already provided should help.
Regards,