I don't disagree with Tarrant, but mapped drives will not work when you are not at home.  Also, if you are using XP Home or even Pro with no server, mapping drives can be somewhat clumsy, but should still be doable.
If your concern is keeping data synched/current, there are third-party data synch tools (LogMeIn Pro, again, will do this for you) that could make this feasible.  If your concern is direct access to the live files, you could employ a combination of file sharing and FTP.
I still say the best way to do this is LogMeIn.  It's free (as is VNC).  It uses uses 128-bit AES encryption over SSL (or maybe it's 256-bit? I can't recall...) and provides drag-and-drop file sharing, background access to processes, services, the task manager, and some performance metrics as far as I recall, and also simplifies printer sharing.  You could also use LMI to provide remote streaming.  I don't know that VNC does these things, but maybe someone who knows more about it could chime in.
I would also caution against using FTP unless the data is not important or senstive.  FTP over an open connection is not secure; sFTP is but can be difficult to set up and configure, typically requires a purchase, and by the time you've done it all, it would have been cheaper and faster to buy a year of LogMeIn Pro (it's available for $69.95/year, but can be found for less I think).  Try the demo for free, too.
I will say that VNC wins if you are doing different operating systems, however. But if you're doing Windows-to-Windows, I still side with LMI v. any VNC or simliar options.
Propoganda sheet on LMI:
  
http://www.cadnetpro.com/LogMeInITReach_vs_VNC.pdf
For the record, I can do everythying LMI does without it and save the money, but the cash is worth the time I save and the brainpower I don't have to use (plus I buy a lot of seats for other purposes and get a discount).  The other added benefit for those less technically-inclined is that LMI licneses (apart from the free edition) come with toll-free tech support.
I know that many folks don't like to pay for something they can do for free--but I consider time = money and the cost justifying itself in that regard.  LMI is server-based, so it keeps pace with my ISPs change of IP addresses and eliminates the need to use DynDNS or something similar.
Maybe it would be best to try both for free and see which works?