LAN not working-the default gateway is not available

[swieity]

LAN not working-problem returned

two hours ago internet was working on my laptop via lan and suddenly it stopped working,it is working with dial-up connection but not lan,when i ran network diagnostic,it says the default gateway is not available,what to do? p.s. i am a mechanical engineering student so dont expect me to know a lot about complex things about laptops,please help
after two hour or so the problem came back and now on installing the driver it says this update can only be installed on windows 7...but i have WINDOWS 7!!
below is the screenshot please help!!

 

[swieity]

just got the problem resolved by re-installing the driver

 

[swieity]

what to do??? the problem returned!! and now its not going on even re installing ! should i update the driver?? how?