If you're going to stick with the drill you have, you should try and revive the battery. There is probably nothing wrong with it, but whether you're successful or not will depend on how much patience you have.
When nickel cells are left to self discharge for a long period of time, their voltage curve upon charging again is often wonky, and most chargers will either refuse to charge, or won't charge fully. Here is what it looks like visually:
In this first graph, the batteries had been sitting for over a year unused before being charged. Their voltage spikes up very high very quickly, and in response the chargers cut back to trickle charge after only inputting a fraction of the batteries total capacity.
Naturally, this gives you poor capacity:
This is what you're experiencing right now.
But after some more cycles, things start to look pretty good. This is the 5th charge cycle on the same batteries:
Which results in a normal discharge cycle: