My blog is on my friend's dashboard.

Q: I created a blog while using my friend's computer. Now my blog is on his dashboard. How long after deleting will my blog name become available?

A: Deleting the blog will not make the URL available for anyone (including you). You need to transfer ownership properly.
Make the blog in question into a team blog, with two members, then removing the original team member: http://www.google.com/support/blogger/bin/answer.py?answer=41448

Method 2:
Another way is to vacate the blog address (URL):
1. Sign on with account A (using your friend's ID and p/w) to his dashboard
2. go to settings>>publishing>>Blog*Spot address

3. change the URL (of your blog) to some other name, say xyz1234 (thus vacating the URL)
4. do the word verification.
5. save settings
6. sign on with account B (preferably on another computer): www.blogger.com
7. create a blog
8. choose the name you want as your URL
9. continue to make a post on your blog.
10. publish post

( later on, when you are free, return to delete the blog (xyz123) from your friend's dashboard.)

source:http://www.google.com/support/forum/p/blogger/thread?tid=53b300ad2c9251da&hl=en