I don't understand why you are having problems joining that forum.
Anyway, it's only a must to join so you can download files, it is still possible to browse the forums and check if there are any guides for what you are trying to do.
i did a quick search too
Code:
http://www.modaco.com/topic/355158-r1-superboot-how-to-root-the-htc-desire-c/page__hl__%20root%20%20htc%20%20desire
and
Code:
http://www.modaco.com/topic/308542-r4-htc-desire-easy-rooting-guide-with-tiny-core-linux/
the search of 8181 or "bravo" did not show ideal results, so maybe more digging is needed or that particular forum does not have the guide.
also to answer the initial question "how can i tell if my phone is rooted"
1. install a bash shell and try sudo
2. install a root checker