Fail after boot

do you have the minimum requirements https://help.ubuntu.com/community/Installation/SystemRequirements and also make sure that your iso file is not corrupt https://help.ubuntu.com/community/Installation/CDIntegrityCheck

yea, both iso and computer is good to go!

when i try to install i get a error like cant open dev/0 no medium found

If it can be at any help

got one more error messange glib warning get pwuid failed due to unknwon user id

dont know why but it is only ubuntu that is failing when i am booting because earlier today i installed fedora without any problems :D

Be sure to chack the m5sum of your live install cd... read below...

May be your Ubuntu live install cd is not perfect or it can't be read from your cdrom drive please verify it...

Here some general note and howto:

The main ubuntu site is this: www.ubuntu.com and the download location is this
http://www.ubuntu.com/desktop/get-ubuntu/download

Prerequisites: https://help.ubuntu.com/community/Installation/SystemRequirements
Please also be sure to read the release notes: https://wiki.ubuntu.com/LucidLynx/ReleaseNotes

1) please download the 700 mb file http://www.ubuntu.com/desktop/get-ubuntu/download simply press on download button
To avoid download errors please prefer to download the desired ubuntu iso install cd image using the torrent protocol.
2) check the md5sum of downloaded file to be sure it have no error https://help.ubuntu.com/community/HowToMD5SUM

Only if the md5sum number match with this: http://releases.ubuntu.com/10.04/MD5SUMS go to the next steps otherwise
install a torrent client i suggest you http://deluge-torrent.org/ if you are using Windows and download the iso using a .torrent link from here:
http://releases.ubuntu.com/10.04/ubuntu-10.04-desktop-i386.iso.torrent

3) burn the iso image onto a cd, to do it install and use http://infrarecorder.org/?page_id=5
4) insert the self made install cd into your pc cdrom drive and reboot your pc. You must not see Windows starting and you can try Ubuntu from cdrom and then install it

If you have trouble with installation (the system freeze or you can't complete it) be sure to read the above suggestions, then:

1.a ) Please boot entirely (you must not see windows starting) from Ubuntu live install cd and when the system start to boot from cd you will see two bottom screen icons (keyboard and man inside circle ) please press space (choose your desired language) then a screen textual center menu will appear to you with this items in it:

Try Ubuntu without installing
Install Ubuntu
Check disc for defects
Test memory
Boot from first hard disk

Please select "Check disc for defects" and press enter to test if your cd-driver can read in a good way the live install cd... or if the install cd have some defective file in it.
Then please also perform a Test memory to be sure your pc RAM memory have not any issue

http://www.ubuntugeek.com/how-to-fix-ubuntu-10-04-lts-lucid-blank-screen-at-startup.html

---- Trouble with intel8xxx graphic cards:

please try this: https://wiki.ubuntu.com/X/Bugs/Lucidi8xxFreezes