Yeah as long as you have good third party anti virus and firewall software there is no reason that you have to upgrade to 7.

I hear Microsoft is really upset that more people aren't ditching XP, hey you know what Microsoft in this day and age there is no reason to upgrade your OS every 3 years because pretty much everything that comes with a new OS can now be downloaded in the form of an update or third party software. Unless there is a huge leap in computer power a new OS isn't needed any more, adjust your business model to reflect this.