Don't know all the answers, but I'll try:wink:.
I don't think your firewall is affecting your ability to browse other hosts. If the firewall icon isn't showing and you can d/l and u/l ok then your connection should be good. Don't know why XP's firewall won't start on reboot.
I rarely if ever can browse someone uploading files from me. Try browsing from your search results window. I have much more success browsing that way.
Not sure what you mean by being more exposed being an UP. If you mean exposed to the authorities, I'm not sure, but your isp can track what your doing reguardless.
One reason that UP's tend to have fewer files(though not necessarily) is LW picks hosts who have the extra bandwidth available to be an UP. So hosts with less files tend not to be uploading much so they have more spare bandwidth. So more likely to be an UP.
Hope this helps, though I'd pay to see someone eat their own head
.