You can use photobucket, shutterfly, or flickr. I'm sure there's more sites, but those are really the only ones that I know of. But you have to create an account on one of those sites and then it will tell you to make an album. Once you create an album you can upload whatever pictures you want into the album. It will have a "browse" button to browse the files on your computer and just select the ones you want to upload to the website. Once they are uploaded you'll be able to see the pictures and each picture will have an IMG code below it that you can copy and paste the code into a thread/post/siggy, etc. Hope that helps!
Just make sure you don't use the HTML code because it will not show up since this site doesn't allow HTML.
Photobucket, in my opinion, is the easiest one to use though. What security program are you talking about? Were you trying to do this while at work or something? Any normal virus/security program shouldn't block it.
Image hosting, free photo sharing & video sharing at Photobucket --- try it again!
You can PM me if you need more help. I'll be around all night!