I have several Windows NT servers hammering away and they have been for years. My motto is why upgrade when everything is running smoothly. I have purposely not re-booted several of the servers for up to 6 months to see if they could hang. This gives me good ammunition when I am having discussions with Windows bashers. Turns out that these NT servers have been super champs and have never let me down. They are not fancy Raid systems but home grown machines running a slab of IDE drives. The machines continue to be great multi-taskers as one of them runs a proprietary web server with nearly 15 other task active at all times. There is some hardware that is a bit older that are not compatible with newer technology. But it is amazing what you can find out on the net in the way of hardware deals that companies have tossed.
If you have applications that are running fine on NT why risk the upgrade and get stuck with applications that are no longer useful. [ZDnet]