Can not see external hard drive

I have an external Maxtor USB 2 120GB Hard drive. I was using it as an
archive for software. I just replaced the master drive in my system and
reinstalled Windows XP Pro. What I found was that the system could no
longer see the external hard drive. I went to the Device Manager and could
see no problems. I have Service Pack 2 installed with USB 2 drivers
installed. Windows Explorer and My Computer would not show the external
drive. Yet it appeared it was being detected as I plugged and unplugged the
USB cable. I went into Disk Management and the external drive was being
listed as unallocated space and was assigned a drive letter. I know that if
I format this space so that it is recognize, all data will be lost included
dozen's of programs that I had purchased. I am hoping someone has a
suggestion as to how I can recover the software stored on the unrecogizable
external drive. I have even disconnected it and placed in on anyother
computer with the exact same results. Any help will be greatly appreciated.