if i install ubuntu from windows 7 will i be happppy?how much difference is it, compare to fresh install?

Do you want to replace windows or dual boot?

I don't think anyone else can predict your happiness (grin).

You can boot to the Ubuntu CD without installing it and take a look around.

Unless you are addicted to commercial Windows games or certain proprietary software (such as AutoCAD), you will likely find everything you need in Linux.

Remember, though, Linux is not Windows; it doesn't work the same way under the hood. It is no more difficult than Windows, but it is different. There is a learning curve.

Just a personal view, as a recent convert to Linux. Until very recently, I would have said there was a very good chance of moving to Ubuntu from Windows 7 making you happy. But I would say, it depends which Ubuntu you plan to move to. Getting to know Ubuntu with version 9.4 was for me a great pleasure and a happy adventure. I moved up through 10.04 and 10.10, and things got even better... but since upgrading to 11.10, things have gone downhill very fast. I repeat, this is a personal view, and I'm no expert -- but maybe the fact that I'm NOT an expert makes my view worth more to a fellow non-expert? It really does seem to me that some very bad decisions have been made about the design of 11.10; it has just got much much harder to decide for yourself how you want to organize your work-space. It also seems to me that everything works much more slowly now, which may not worry those with superfast machines; also, again this is personal experience only, but quite a few things which were working fine on my previous installations now work unreliably.

My advice? Move to Linux, wholehearted recommendation, the Linux world is brilliant, a real joy!!! Move to Ubuntu in a 9.xx or 10.xx version, for sure!!! Otherwise, consider a different flavour... I seem to gather that the other obvious "people's choice", Linux Mint, is beginner-friendly too. Ubuntu 11.10 is not.