If I format this Hard Drive I will lose ALL my needed files

I'm having some problems with my 5 year old Seagate Hard Drive in my new GXT Brand external IDE USB external enclosure. I installed in my old Seagate Barracuda IDE drive (filled with needed files) the new enclosure (it doesn't appear to have any place to adjust jumpers) just the 2 perfect fitting plugs. The software that came with this external enclosure said Windows XP didn't need any drivers. Both old HD and the computer I’m currently trying to open this HD both used Windows XP.
The new enclosure/ drive is recognized in "My Computer" as H (there is currently a C & E) but when I clicked on it to open it, it said the drive is not formatted.
The problem is if I format this Hard Drive I will lose ALL my needed files on this HD.
This 5 Year Old HD I'm trying to open (filled with needed files) came out of my Dell desk top that was corrupted by a bad executable file (Hijack and blackmail) rendering the operating system useless after the virus remover deleted needed infected program files.
Any Ideas on how to save these files in this hard drive? (By the way there is NO security Tab under this drives properties).
Yes, I know I should have had a backup (too late now).
Could anyone extract these files from this HD with some pro tool that an amateur like myself doesn’t have?
Any help suggestions would be greatly appreciated.
Thanks!
Duane

HMMM,you could/might install it as a secondary drive after your current primary hdd [slave it with cable select] OR,, you could go to www.majorgeeks.com and look around ,lots of goodies there..