Follow the instructions when you set up your new system, as soon as possable make a set of recovary discs.If the option does not appear look in "help and Support " on the menu and it will tell you how to do this,normally you need 3 4.7 DVDS then keep them safe you can normally only make 1 set but can also purchese a set from the makers
You can normally connect your Virgin modem and it will connect. Partions will normally be in place on a new system,whatever you do do not interfer if there is a partion for recovery.
You may well find a lot of junk is installed by the makers, inc a lot of trial programs. A lot of people remove this but be carefull what you remove.
Whilst you do have your docs etc copied onto external drive. see what installation discs you have for your programs such as word processors etc they may not be the ones you have on your new system.
From the file options on IE save your cookies fav to your external drive, also dependent is what e mail you use Outlook express does not work with Win 7 So save your contacts. address book, and any emails you wish to keep.
As you will still have these on your old machine this can be doen at a later date