We use pcAnywhere very heavily, and love it. Its on our front counter pc, wizard pc, 2 home pc's, laptop, and 3 other offices where I work certain days each week. I can access any of these places through the internet, from any other location. We do it via internet(cable), not by modem - the program can use either method.
In addition to daily POS (data only) backups at the shop, pcAnywhere is used every weekend to back up the shop server's data (full POS program directory, documents, and quicken) to the house. It only takes a few minutes to do so, and it gives extra piece of mind.
For pcAnywhere to work, it has to be installed on both machines. (the one "calling out"(remote) and the one "receiving the call"(Host)) If you are using a router, you'll have to forward the ports (5631 and 5632 are the defaults) to the appropriate internal IP address of the destination machine. In addition to requiring software on both ends, you'll also need to define encryption and security (login name and password). These are required before the host will grant access.
Windows XP has a built in remote control application, although I haven't personally tried it.
If using pcAnywhere with XP, make sure its version 10.5 or 11.0 I have both and prefer the 10.5 version. (version 11 sometimes corrupts files when you do a file transfer). I might be biased towards 10.5 because I was one of Symantec's 10.5 XP beta testers
Mike