using internet on a mac with windows

[MiladGh]

Hi.
i have DSL internet. which i can create an internet connection in 2 ways (an always connect mode and a creating a connection mode).
right now i have a pc. only 1 operating system and it works ok.
the question is:
if i connect my mac to internet and i use an emulator such as "parallels" or "virtual box" to run windows, will i be able to use the mac internet on them? or should i create a connection for them separately?
and 1 more question! if i use a windows software that manipulates the internet connection on windows, (changes proxy for example) will it affect mac connection too? can i use such software that runs in windows with my firefox on mac? can they work together?