How do I tell it which directory to use?

From Tom:

In R 2.2.0 under Windows, I want to be able to give it a filename such 
as "myFile.txt" without the quotes. But actually I mean:

C:\Documents and Settings\Tom\My Documents\qpaper7\R Project Started 
19 Dec 05\myFile.txt

If I were to repeat this each time, my computer would get all bored 
and cranky and start to drop bits (only a joke, of course). I think I 
want to set the Home directory or the working directory or some 
directory or other to the above directory. I may or may not want to 
set some environmental variables.

R 2.2.0; working directly from the console and copying and pasting 
code which I want to test into the console. Windows XP Home Edition. 
Administrator privileges are enabled. A curve ball: There are two 
accounts, "Tom" and "Jones;" the data are stored under "Tom," whereas 
the computation is being done under the "Jones" account. I won't bore 
you with the details of why I am doing this.

I was able to call Sys.getenv ("R_USER") and get the home directory.

I am a newbie to R and not familiar with the terminology.

Tom
Thomas L. Jones, Ph.D., Computer Science