More help with 'images' needed please!

I'm sure this has been covered before but help would be appreciated.

I have been trying to add a 'picture' which someone kindly made for me to my signature.I have it stored in a file in 'my documents'.I tried to add it using the browse feature below the signature box, but it just says it is 'unable to save image'.

I tried to 'insert image' within the signature box by cutting and pasting ...and although the image appeared and I saved it,my signature now shows a little box with a red cross,so obviously I've done something wrong.
Can you point out the error of my ways?
Thanking you in advance

I'm sure I had the same problem and the only way I could get my signature to 'take' is by hosting it on the web. There are several places that do this but I use www.xs.to Another popular one is www.photobucket.com

They are free and simple to use.

Thanks Tiger....I have been having a little word with kingetter ( quite a few actually..I have an awful lot to learn!) and he has got me 'sorted 'once again.
Thanks again...to you both!:D