Can you still write programmes for PC in assembly language? Answered

Is it still possible to write programmes that will run on a normal PC in .asm ?

I've had a look around, and the little information avialable seems to only be relevant to pre-1990 PC's running MS-DOS.

Does anyone know of any sites with more up to date information for the processors/instruction sets in use, or what assemblers and linkers are available?

Any help would be appreciated.