The bulletin board software is vbulletin. See
www.vbulletin.com for more details.
The database is mysql.
There are also quite a few programs which run on the server to make admin easier, handle advert stuff, etc.
The operating system isn't from Microsoft.
The hardware is a 2-CPU Intel box with 512Mb of RAM and 9Gb of fairly fast disk. In the very near future we're moving to a machine with about twice the CPU speed, twice the RAM, twice the disk space, ...
...Mik