This process can only be done if two pc's are connected by one router to internet. You need to create a home network in order to see the other pc's folders and then copy the contents to the other pc.
First you need to create a network between two pc's: Homegroup - Add Computer or Join
And then you need to locate those folders that you want to share with the other pc: File Sharing - Between XP and W7 (and vice versa)
Once its done then go to the Windows explorer of your pc running Windows 7, on the left hand side click on the Network icon, there you should see your other pc's name, double click it, and you should see the folder you shared.
iCloud or other cloud programs are also a possibility but it depends on how much files you want to transfer. I believe iColud offers 5 Gb. The other options will be to burn them on dvd discs or use an external hard drive to carry them from one pc to another.