I am afraid that your post is very hard to understand. May I suggest that, if English is not your primary language, you use Google Translate?
If you want to back up your XP machine to an external hard drive and then install win7 on your machine, you can expect to spend about $110 - $125 for a 2 TB drive. You may be able to do with a smaller drive; how big is your system hard drive?
Again, if that answer is not relevant, please provide more detail. Thanks.