Susan,
Any of us would be more than happy to help with your networking and/or remote connections. While there are many topics on this board, by far the three most discussed are backups, PC to Fax and Fax to PC, and remote connections.
A quick search of the word "Remote" will bring up four pages of hits. I am sure other key words will do more. My advice would be to pore over these before we try to reinvent the wheel so to speak.
Without going into any detail, it is best if all of your users can remote into the office that has the network and use any of the PCs that are connected to the main database. Again, many options, but LogMeIn is the simplest and cheapest, i.e. free.
There are ways to sync your data, but I have found it can be fraught with problems. Also, there is a new sync system in version 4, which I am guessing is better and easier. Unless you do not have any way of connecting to the Internet from your remote sites and/or have a lot of off site work, then I wouldn't necessarily recommend syncing. But, I wouldn't completely rule it out either.
As to firewall issues, what types of software firewalls are you using? Are you using a hardware firewall such as Linksys, Netgear or Cisco? My only other recommendation would be to upgrade to XP Pro when you can and to only purchase XP Pro in the future unless you decide to go Vista.
