Issue converting to number

Hi

I have a large list of numbers and need to use the VLOOKUP function with them but all of them show an error which offers me to convert them to numbers. When I select it the error is gone and the formula works, yet under the category of the cell remains as general. In order to correct the other cells I changed the format to number but the error thing still comes up and offers me to turn them into number. I remember I saw someone selecting the list and choosing an option that said "convert to number". Can anyone please tell me how I can do this?!

Thankss

EDIT: Never mind I managed to fix it :D

http://www.quepublishing.com/article...7553&seqNum=11