Fitzitz :
What do you mean by "a lot of data is lost"? If you are building a new PC, the only thing you are losing is the old OS, and if you call Microsoft you can usually get a replacement key for free.
Edit: And if you don't use the old hard drive, obviously any data on there is lost too lol
i get that but i was thinking of backing up a lot of photos , music , videos and software
a few people told me that you will have to get all the drivers and software and stuff like that all over again , is this true ?