Be careful, be very careful!
If you open up your machines to access via the Interweb, make very sure you have an excellent firewall and that it's properly set up. A friend of mine got home one evening to phrenetic flashing lights on his PC and router. He'd become the unwitting download source for a porn site. He got some pretty nasty hate mail and worse when he turned it off.
I run "Remote Desktop" on my Windows machine, VNC on the Linux box, and remote access on
the Router- but that relies on Draytek's NAT firewall and ZoneAlarm. ShieldsUp! reports "total stealth" on the system. Without those safeguards, don't risk it!
Remote Desktop (free with XP) does the job.