Question: OK, so i just need a little advice. I own a Fujitsu Esprimo Mobile v6535 machine with these specs:

4GB RAM
Pentium(R) Dual-Core CPU T4300 @ 2.10GHz × 2 
Unknown graphics driver (found somewhere on the net i have an Intel GL40 chipset and Mobile
intel®GMA 4500M graphics )
500GB disk

Will it run smoothly according to these specs?

Do You want to Ubuntu12.04 as dual boot or you want to install after removing existing OS if any.

Answer: 
Yes you can. But I would go with Ubuntu 13.04, specially if it will be the only OS on your system. For more info about 13.04 check out the [Release Notes](https://wiki.ubuntu.com/RaringRingtail/ReleaseNotes) 

To download 13.04 [32Bit](http://ftp.ticklers.org/releases.ubuntu.org/releases//raring/ubuntu-13.04-desktop-i386.iso) or [64Bit](http://mirror.sov.uk.goscomb.net/ubuntu-releases//raring/ubuntu-13.04-desktop-amd64.iso). 

If you have a reason for using 12.04, then you can download the [32Bit](http://mirror.as29550.net/releases.ubuntu.com//precise/ubuntu-12.04.2-desktop-i386.iso) or the [64Bit](http://mirror01.th.ifl.net/releases//precise/ubuntu-12.04.2-desktop-amd64.iso)

Once you download the release that you like, you can burn 12.04 to a CD or 13.04 to a DVD. Also you can create a bootable USB if you so desire.

If you decided on 13.04, then you can check out the [Install Ubuntu 13.04](http://www.ubuntu.com/download/desktop/install-desktop-latest) website.

If you decided on 12.04, then you can check out the [Install Ubuntu 12.04.2 LTS](http://www.ubuntu.com/download/desktop/install-desktop-long-term-support) 
website.

Both of these site have all the information that you need to install, burn your media, and how to create a bootable USB.
Yes, should be just fine... I'm running Ubuntu on a compaq 6710b, Intel centrino and 2GB of RAM... 

have a look at this: [Installation/SystemRequirements](https://help.ubuntu.com/community/Installation/SystemRequirements)