I use a program to ftp stuff to websites... and have a big upload going on. While uploading, the program cannot open other files and do other tasks.

In Windows XP or Vista can I somehow open the software again and use it separately?

Really depends on the app itself.
Some don't allow more than one instance running at a time.
Maybe a simple case of switching apps.
I use SmartFTP for this kind of work and it will allow multiple instances, best of all it's free for non-commercial use.

FYI, Filezilla is a nice FTP client too

It works for me when I send coloring books in PDF. I just open another window and log on again, so I know that YouSendit.com works.

http://smileys.smileycentral.com/cat/15/15_9_16.gifP.S. Hi Curley and RickJ