Hi.
Nowadays it is easy to switch internet (compared to dialup etc - which I am guessing you don't have). You got a broadband modem? The you should plug in the ehternet cable and XP will hopefully recoginse the network omn its own. If not you may have to use a wizard to set that up - but its easy!
As for your printers and other hardware. They will need reinstalling. Got the driver CD's..? Then you just follow their instructions. Treat them as if you have only just bought them and opened the box. The fact that they have been on another computer makes no difference.
For your files then you can get a cable, or burn them onto CD, transfer to a USB drive etc. Thats by far the easiest way. Do you have virus protection on your old PC? If not download AVG 8.0 Free Edition and scan them as you don't want to take any hidden virus onto your new computer.
Finally, your forums etc. Your passwords and favourites are stored by your browser (Internet Explorer, Firefox etc) and on your computer. You can download a programme to transfer them but ist probably not worth it. Just re-enter your passwords and save them as favourites the first time you visit them on your new computer. It is a good idea to delete your tempoary internet files and cookies when you finish with your old computer, or click "Forget Me" or whatever on the webpages..
Hope this essay helps, Doug.