Ubuntu kernel replacement problem

[cosmophobia]

Hi all
i don't know where to start exactly ...
First i am kinda newbie in Ubuntu. I am working 7 months with Ubuntu and still i have many difficulties. I went through many problems and still i succeed to fix them all ... but here i am on my way to give up...

What have i done ? Well simply i have tried to update my system with "apt-get". Afterwards i saw a message "0 to install 0 to update 3 not upgraded". These 3 were linux-generic linux-headers-generic and one more. I have done this ... and suddenly i have chanched my kernel to the last version.
After rebooting my machine the worst happened - i had no GUI, no graphics at all.

What the real problem is ? The problem is that i am student in IT engineering, where we work only and with Windows OS and ( isn't that funny?) and Windows Servers. However i preffered to use Linux because of the growing popularity of open source OS, because with linux i have more opportunities to learn new stuff and of course because i hate Windows the most . My problem is that i have 4 Virtual Machines in VirtualBox inside my computer.I still can see the files and i still can operate to some level. I have minimal graphicál interface in "xterm" mode. Yes but i can't operate with them in "xterm" mode and that is so crucial for me. I have projects to make and i am depending of my virtualization. I don't want neither to change my beloved Ubuntu (if is still Ubuntu) and i can't risk to lose any data inside my computer. I will describe the steps i took in the next chapter of the thread !

[devils casper]

Hi and Welcome !

Which version of Ubuntu are you using?
Boot up in Command Line Mode and execute startx command. Post error message here, if any.