Help With Ubuntu Ultimate (fiesty)

Hello Computer Geeks, Today, I won't teaching but I will be asking (we all learn don't we )

Now, here comes the q? :

Well, I seem to be on the run, so here's a brief question. I think the answer should be simple for Ubuntuans

I have just installed Ubuntu on a FrEsH 40GB HDD, and I slaved the other 20GB in the System .
I also have another Computer on my Network and I have about 15GB I will like to backup, So I need tu access shared folders on any of Operating Systems,

On Ubuntu, I pressed [Alt+F2] and I got the box tu connect, I entered SMB://xxx.xxx.xxx.xxx (My I.P on Windows XP PC),
i progressed because I could see my Windows Shares but when I try to open any of the folders, Ubuntu demands a Password, I entered all usernames and passwords on both Computers but no progress, the Username/password dissapears and pops up again . .

What do I do? ?

hi, do u have the administrator password to all the system.