Nickmo's correct - it's not an ISBN. However he/she seems a little confused about how the 10 and 13 digit ISBNs work.
The old standard is 10 digits. However, there were too many books being published for this to continue to be viable, hence the change to 13 digits. The book trade has been using both for the past few years in an overlap period, but the 13 digit became standard on Jan 1st 2007. Many systems can still use either, but I've noticed using 13 on Amazon doesn't return anything, even though they have the 10 digit listed.
You can't just stick 978 on the front of a 10 digit ISBN to make it a 13 digit one. It doesn't work like that. Many do work like that, but not all.
Eventually, the old 10 digits wil be phased out, but I reckon it'll be a while yet.