Jaguar has an option to overwrite the drive with zeroes, which would technically amount to erasing the drive. It is still possible to get past this and see old data, though.
To "securely" erase a drive, you have to overwrite it with random data several times. I think there is software to do this on Jaguar, but if you're going to be throwing your money at the problem, you may as well pick up Panther, which has the option built into Disk Utility.
On the other hand, I can't think of any good reason at all why your boyfriend should be worried about Russian spies seeing what the other guy used to have on there. If the previous owner didn't see fit to protect himself, why bother?