I have used maybe 30 distros and as time goes by Linux gets a bit better in hardware recognition and networking.

Now I have a Win XP machine thats the gateway to my USB back-up HD and Canon MX310 Multi print/scan/fax. If I want to connect a new computer in this network I do two things, Put the computer in the Group by filling in the group name and check with the new machine thru the new network the XP machine and install the printer by clicking on it and all is set.

Witch disto can do the same as simple as this without installing all kinds of software? And is usable as a desktop pc. Oh one more thing, I don't like the taskbar in the upper side of the screen. I like DreamLinux but ...

It has to connect with all win versions.
And Canon Pixma MP150 driver does not work on fax and scanner (only printer)

UPDATE:
It has to run lots of custom business Windows software

That is incredibly easy to take care of. Just right click on a blank space on any of the panels and I think you can figure it out.

The panel is actually just another application, and you can add applets to it (including start menu, tray, taskbar, etc.)

That I know, I mean I do not like the way Ubuntu has it done

What do you mean? I just told you how to change it!

You answered 1 question but not the main question.

Witch disto can do the same as simple as this without installing all kinds of software?

"Now I have a Win XP machine thats the gateway to my USB back-up HD and Canon MX310 Multi print/scan/fax. If I want to connect a new computer in this network I do two things, Put the computer in the Group by filling in the group name and check with the new machine thru the new network the XP machine and install the printer by clicking on it and all is set."

I don't know anything about connecting Linux and Windows computers, so maybe someone else can help.