When you attach a picture to an email/web site do you not go to the folder containing your pictures on your hard drive?

yes, but Picasa will not come up for me. I wondered what I was doing wrong.

If you want to attach a pic to an email you don't need to open Picasa.
Just click "attach file" and you'll get a "choose file" box.
Go to where you keep your pics..My Docs etc and choose.
As I understand it Picasa just "monitors" your pic folders,it isn't a pic folder unto itself. So you can't do an attachment from it.
I hope I understand your problem correctly.

That explanation should be of help to you......also, if you want to embed or link a photo to a website, that can be done directly from picassa by copying and pasting the url address they supply on the right hand side of your album page.

Terminology seems to be getting crossed up and causing room for confusion.

For reference purposes there are two Picasas that can be in play. There is the picasa you have on your computer. As mooner noted you can just click on "e-mail" in there and send a pic by e-mail from there if you want.

Also, Picasa will let you set up a web site account and upload pics from you computer to its web site in your Picasa program on your computer. Then, as referenced above, you can link to other places on the web from there.

Lastly, if you want to store your pics somewhere on the web besides picasa's web site, you have to "export" the picture/file in the Picasa on your computer to another place on your computer, where you can then upload them to, say, Photobucket. At least that is the way I do it.