Yes, you can open them using MS Paint and shrink them down using "scale". Chances are that they have been taken on a high resolution setting rather than one optimized for the internet.
Or, use WinRar to compress a single file into as many files as you like and send each each in a seperate email. The receiver will have to de-compress though. You can use the likes of MS Messenger to send large (or small) files, if your friend is agreeable.
if you are using xp send them directly from my pictures.
highlight photos you need to email then down the side under picture tasks > email this files click on that an it will come up asking you if they will reduce size for emailing.