Now Here are some easiest steps to Install Kernel 3.4.3 on Ubuntu12.04.
Guys! please do install the kernel at your own risk. Installing or upgrading to a new kernel may break your system. Sorry for that
You need to do at first is to download all those necessary files.
1. open terminal by Alt+ ctrl+ T
2. you need to download the required header file of headersall.deb so copy and just paste this command on the terminal
cd /tmp && wget -O linux-headers-3.4.3-030403_3.4.3_all.deb http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.4.3-quantal/linux-headers-3.4.3-030403_3.4.3-030403.201206171454_all.deb
3. now for downloading the header file
cd /tmp && wget -O linux-headers-3.4.3-030403-generic_i386.deb http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.4.3-quantal/linux-headers-3.4.3-030403-generic_3.4.3-030403.201206171454_i386.deb
4. now you need to do is download the image file
cd /tmp && wget -O linux-image-3.4.3-030403-generic_i386.deb http://kernel.ubuntu.com/~kernel-ppa/mainline/v3.4.3-quantal/linux-image-3.4.3-030403-generic_3.4.3-030403.201206171454_i386.deb
5. now is the time to install all those downloaded files. So, lets install them one by one.
6. Install headersall.deb
sudo dpkg -i linux-headers-3.4.3-030403_3.4.3_all.deb
7. Install headers file
sudo dpkg -i linux-headers-3.4.3-030403-generic_i386.deb
8. Install image file
sudo dpkg -i linux-image-3.4.3-030403-generic_i386.deb
9. Finally you are done!!
now you need to do is reboot your machine
sudo init 6
10. after the reboot of the machine you need to do is check the updated linux kernel
so type this command
uname -r
Now you are done. cheers!! :D