We have connected our two computers directly to a DLink Router via ethernet cables ,The problem is that everytime I start either of the computers the Internet connection is unstable or absent. Then I have to unplug the router several times until the lights start blinking properly again and I have stable internet connection back on both of the PCs. This however is annoying and I don't know how to fix the problem once for ever. Any of you guys who has some experience could please enlighten me about what to do..

hmm, what kind of dlink is it? What kind of operating system are you using? Is the router directly connected to the internet, or are you going via another (dsl or cable) router? I would assume that the router is also acting as a DHCP server, so I would check to see if you can ping from one PC to the other without having the internet cable in the router. If you are able to ping consistently without losing packets (if using windows use "ping x.x.x.x -t" for a continuous ping) you know the problem is most likely with the internet connection, perhaps the MTU settings have been tinkered with. In any case, you need to provide much more info.

Since there are so many variables involved in trouble shooting networking problems just do like I did, go to Google and search "home network setup". If that fails try posting in a Newsgroup, there's always specialists willing to help you get it working right.