A lot will depend on your weight. Our sport puts a bit of emphasis on how much you weigh because it makes a big difference in how boards and sails react. You don't want too small a board when starting and a good wide modern board is the best. I'd be looking at somewhere about 130-150 litres with a small sail of about 5 metres as a rough guide.
I'm not pushing any stores (none down here anyway) but some advice from an expert really helps.
Also, a search of the forum for other threads could help because this question does come up often.

hey! good choice to get involved with windsurfing, the best decision you will have made in a while!

keep ur eye on the technique section of boards. Sam is an excellent windsurf trainer in the uk who is giving tips on how to get involved easily. the first section is online here:
http://boards.mpora.com/technique/sam-ross-people-windsurfing.html

i think there will be 5 sections in all with video!