You don't need the W2K boot disk. Download the Win98SE bootdisk (1 floppy). All you are going to do with it is Fdisk, Partition and Format the hard disk. Once that is done you can install whatever Operating System you like on it. Personally I wouldn't go from win98se to w2k though.
Well, I am not pj123, and I would suggest that if your PC has an adequate spec (say, 600mhz processor and 256Mb RAM) then go for Win2k.
I run it with win98 and WinXP and find it the most stable OS that I have. XP is good, but tries a little too hard to be friendly. Win98 is good too, and when updated is stable and runs ok.
But with Win2k, I have not had a crash in years (literally - Jan02 was the last time I got a stop error with Win2k). All it needed was the latest drivers for my hardware (nothing out of the ordinary) and it has run perfectly since. I rarely reboot it as it does not have the resources problems which Win98 has.
And the bottom line in any such discussion is something to the effect that there is also a sense of "je ne sais quoi" with computing and what works wonders for one may often be anathema to another.