Hi,
I think the first question is whether the PC can connect via a LAN cable to the ADSL modem? In debugging, it is best to be sure you have a working connection, and then we'll add things (like a wireless router and card) into the mix.
So assuming you have a connection, something you may want to consider is the authentication method at the ISP. I do not know if this is the case at Netvigator (but believe it was the case at icable) that the DHCP server at the ISP assigns a lease to your account based on the MAC address of the device connecting. It maintains the lease for a few hours, figuring you just went offline for a bit but will be back.
However, if you come back with a new toy in the mix (such as a wireless router, or a VoIP box that has its own MAC address) the central server is like "ok, I assigned this IP to this MAC address, and now there is a new device at that place. WTF?"
I ran into this after installing my wireless router on icable and then, after the fact, trying to add my US Vonage VoIP box. It took a few hours for the central server at icable to reset and reassign a new IP to my device.
But if this isn't the case...then we need some more information.
So you plug your computer into the modem via LAN cable and it works? Yes (if no, then this is an ISP level issue). Ok, so it works. Now you plug in your wireless router. Is it properly configured to pull a DHCP address? Is there any authentication required? You will probably have to put that in and all that.
On your PC...can you see any other wireless networks? Just stick the thing in your window and see if any other networks show up. If you can get online via the LAN cable grab a free program called "Stumbler" which will help you find other networks.