good luck resizing a jpg in paint, unless you got a conversion plugin.
lview is a pretty good free photoshop kind of tool. of course you can also resize pictures that are uploaded to photobucket which is a nice handy place to keep all your online shares. that way every picture you have posted in pretty much any forum can be deleted instantly by deleting them in photobucket. makes me feel a little better during those tense paranoid days.
however if you would like a free online photoshop, try
Online image editor pixlr free - fix photos direct in your browser just click file, open like you would on a regular app and it will upload the picture to that site and let you edit away.