If you use the Search box in the Start bubble, type in %Temp% and that should find the Temp folder.
But I don't do that. If you are talking about email attachments I never open them directly from the email as I can't be sure they are virus free. Instead I right click the attachment, select "Save as", then save it to some convenient temporary location, (I use my Desktop). I then right click that file and scan it with my anti-virus. Only then do I open it if it comes up clean. That way I have a clean file already saved.
With Win XP I can go to the temporary internet folder and find the latest file I recently OPENed from email.
I can just copy it and save it some where else for later use without going back and SAVE it from the email again. This saves download time, especially for large files.
With the Win 7 of my new laptop, I just cannot find it. Where is it now?