Connecting two pc to a single ISP account

Hi all,

I am struck in a situation to which i have no solution.

i am describing my situation as below

i have 2 pc :- 1) running win 7 and having Realtek PCIe GBE Family Controller ethernet adapter
2) running win xp and having a Realtek 10 MBPS PCI LAN Card
I have an ISP named TIKONA which provides me service as this:
1 It requires login whenever a user tries to use internet - (The user logs in and is provided with an ip and the login is effective for the time the internet is being used and then the ISP logouts the account after 10 mins. of inactivity. )
2 It allows us to make simultaneous logins from different computers.

So what i wanted to do was to make a lan of two pcs and make them use a single account with a single login to access the internet / In other words I want a network where I log in from one pc and the internet is available to the other pc also.
Yes, I know this is very simple

But MY ISP's configurations are different from normal ones.

I have connected 2 pcs to lan ports of my router and connected the internet cable {from my ISP} to the uplink port of the router.
Now when I login from the first pc and move to the second pc and start the web browser the login page of the ISP pop ups . In simple words the ISP wants another login for this pc.

But I want to login from first pc and and then use internet on the second pc without logging in.

Please suggest me how should I connect my pcs and the router so as to gain the desired situation


Thanks in advance