i have a load of photos taken onto an sd card that are all in black and white(shot that way) is it possible to convert them to full colour? ta

Simple answer is no....

Complex answer is.... yes in theory it is possible but I dont know of any openly available software. Some specialist companies have written their own algorythms to do this but the photos require a lot of touching up afterwards. A few WW1 films have been converted into psudo colour this way.

If you google it, there are a ton of "how to's" on it. Mainly using Photoshop. I'm not sure about linking other sites and what that's like with the rules, so i wont do it, but yahoo answers has a few nice ones!

You can add colour using e.g. photoshop. However since there is no colour information stored in the picture this will be a manual process and any colour you add will be based on educated guess work.

I always shoot full RAW that way B&W can be done in post production.
Some B&W functions can retain enough croma information to convert back but most use luminance from each RGB channel combine and throw away unwanted info to reduce file size.
I did in the dim and distant past use multiple exposure B&W image layers then pass red,green & blue (cyan, magenta & yellow) through individual layers to produce a colour image, (this technique is used in astro photography) but it is very time consuming and in an image with people your brain will find areas that don't match it's expectations easily.
Interesting problem though.