New Mac User - Networked PC's just dissapeared from my IMac

Hi all,

Firstly, it's great to be here and even greater to be a mac user after using pc's for the last 10 years.

So I splashed out and bought a 27" Imac on the weekend, and have to say - overall, I'm extremely impressed with this machine.

So on to my problem,

I plugged it all in Saturday afternoon, booted it up and away she went. After the initial set up, I was delighted to find that the Mac had already mapped my 3 other pc's, and I could access them from the tree on the left in the main window where you see mac hdd, network etc.

I thought this was fantastic that the Mac would automatically do this. Anyway, I spent most of Saturday installing all the programs and software I purchased and then decided to copy my music and photo's accross from my win 7 machine.

I jumped back into the window where I could see all my other pc's, but they had simply vanished????

Now, the only way I can get back into them is by going to "Connect to Server" everytime I start the mac up.

I'm hoping one of the experts here can assist me in why, how, or what I have to do to get them to come back and display like they did automatically.

Thanks guys.

DS