Use a sharp knife to slice down the joins in the battery pack. use a screwdriver etc. to separate the halves (be careful!).
Remove the cells. Note the polarity and placement of the metal contacts. Really note it! If you get it wrong you'll be sorry.
Get a new pack made up (or make it yourself from 4 sub-C nicads with solder tags).
Connect the V shaped contacts (are they the right way around -- polarity).
Make sure the bits that sto pit all shorting out are in the right place.
Note that the 4 cells are arranged in a rather non-conventional way, so if you get a pack made up from 4 cells, make sure they make it the right way!
Place cells in shell
cover with the other half
check polarity again (Just because you're paranoid it doesn't mean you're wrong).
insert in device (printer, HP97, etc)
charge briefly
turn on device (does it show some life?)
charge it completely.
There is no real need to glue the halves back together again. They'll stay together in the device. Otherwise pich the adhesive of your choice (but pick something you can disolve later if you need to re-rebuild.)