Mac to PC network problem help

Okay I got a little situation with my Mac connecting to my PC. When I first bought the macbook it work perfect with my PC. I was able to connect to my desktop network and share files.

After I reformatted my PC, I was unable to connect to my desktop. The macbook was able to see the my desktop, but after entering the username and password a screen pop up saying something about the folder are not there and I need to fix the alias.

Then I just updated to leopard today and I tried to connect to my desktop, but I was unable to log into my desktop even though I use the same username and password. doesn't matter I use username or guest account. I just get a message saying I have no permission entering this server.

So I was wondering is there anyway to figure out the username and password incase I enter the information wrong somehow when I reformatted my PC.

any advice is appreciated.

 

Yea its enable on the pc. My sister's xp laptop can connect to it, so i'm kinda clueless here.