If you don't have a cable you can just email them to yourself and print from the computer.
If you need to print them as proper photos I think the photo booths in the likes of Boots or Tescos have docks to link up to iphones so you can print directly from there. Or save to a memory stick before you go.
Are they pictures you have taken with the iPhone's camera? So that they are on the Camera roll?
These are fairly easily transferred to your computer so you can print them from there.
I have Vista, but afaik, the procedure in XP will be similar.
Open My Computer & connect the iPhone with the USB cable. When the iPhone appears in My Computer, right click it & choose Import Pictures. They will appear under Pictures in a folder with today's date.
You may also find that when you connect the iPhone you get an AutoPlay dialogue box, with one of the options being Import Pictures - you can use this if you prefer.