Hope this helps!
make sure you buy a wireless router, aka make sure the box has the word wireless on it. Also consider whether you want to buy an apple network device (not to rule out Time Capsule, in addition to airport express and extreme) The nice thing about apple network devices are that their interfaces are built into native OS X apps, giving it the nice Aqua (OS X's graphics user interface or GUI) appearance and (in my opinion) assurance. I personally find that interfaces are not just pretty, but overall less clunky and more concise than those of other 3rd party routers. Back to Time Capsule, which is a apple router and an NAT drive all in one....time capsule <3 's time machine, OS 10.5 automated backup utility. This way you are forced to backup...hehehehe. This is a very very very good thing! In addition, if you are not interested in time capsule or an airport extreme (which has more functionality than the express) look into whether or not your computers, including the pc's are 802.11n capable. If ONLY 1 OF YOUR COMPUTERS ON YOUR WIRELESS NETWORK IS G/B, YOUR ENTIRE WIRELESS NETWORK WILL DOWNGRADE TO G SPEEDS!!!! I work at an apple reseller store and we sell g airport expresses, not sure if apple stores do. But if you do have g computers and don't plan on upgrading to n capable machines in the near future, do yourself a favor a save a little bit of money by buying a g airport express. sorry if this is a little bit jumpy, contact me if you got any questions!!!