Windows v.s. Linux - (OS)

Windows or Linux.  Well this may surprise you but I am not taking sides.  There is no all encompassing correct answer, the right answer must be tailored to each situation.  A typical Windows installation is expensive but the money you save by getting a free copy of Linux may cost you in labor (and depending on how much of a clue you have, you might spend a lot on aspirin).
Now days both operating systems are very stable.  Reboots are to a minimum whenever you add or upgrade, but Windows still requires more reboots in that respect. Both provide very comprehensive security and stability update notification services.
The largest difference is migration.  To move from one Windows server to another, you must build the new server and then create each instance or object and then import the data.  With most Linux services, after building the new box you just copy a few config files and the data.
If you still have not decided which operating system to go with, first inspect your checkbook and then go on to read the Windows 2000 Server installation guide and then the Linux Installation Guide.  Hopefully this will be enough mental punishment to force you to a decision.