Comp crashes and refuses to boot from cd or flash drive

I think the problem is with USB drive, it is not able to deliver the files fast enough. Try using live CD.
If you want to install ubuntu, first back up your data on external hard disk and live CD of ubuntu not USB, because some time the speed of USB do not match the requirement of computer to get files and due to missing of files the system used to crash.
Make a Live CD and Reformat your disk/ clean installation of ubuntu/fedora etc.

Also never go for upgrade any linux version to any other verson. Infact if you want to upgrade from old ubuntu to new it is recommended to install a fresh copy not upgrade.

Please be sure your ram is good boot from Ubuntu live cd and press spacebar when you see the man in the circle bottom screen icon and select the item to check the ram....

I tried to use live cds...ive tried linux mint 7 live cd, fedora 13, openSUSE 11.3....and my computer doesnt want to boot any of them.

Please tell us the model and brand of your pc, then please modify, by entering into your pc bios settings the boot sequence...

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Here some general note on install Ubuntu and howto to get a good ubuntu iso cd image (.iso) to burn on a cd:

- Here the steps to install Ubuntu 10.04.1 https://help.ubuntu.com/community/GraphicalInstall

- Here install Ubuntu video http://www.youtube.com/watch?v=XaqaDZZ_P0g&feature=fvw

Below there are some intructions to:
--- 1) Ubuntu prerequisites... and Ubuntu for pc with low power
--- 2) download the iso...
--- 3) check the md5sum of the iso image, please don't forget to check...
--- 4) burn the iso image to a cd ...
--- 5) install Ubuntu using the self made cd ...
--- 6) trouble screen at installation or at first boot after installation ...
--- 7) Ubuntu manual and online help...
--- 8) Relax and fun...

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

--- 1) Ubuntu prerequisites: https://help.ubuntu.com/community/Installation/SystemRequirements

Ubuntu 10.04.1 release notes: https://wiki.ubuntu.com/LucidLynx/ReleaseNotes

https://wiki.ubuntu.com/LucidLynx/ReleaseNotes/ChangeSummary/10.04.1

If your ram is less than the recommended amount, you won't be able to install with the graphical installer,
but you might be able to use the Alternative cd, where you can use a text based installer - that uses less memory.
If your machine does have plenty of ram, you might want to try running Memcheck (which is also an option from the live cd, see below)
to just make sure your ram isn't failing.

- if your pc doesn't meet the Ubuntu prerequisites, you can try:

xubuntu http://www.xubuntu.org/get
lubuntu http://lubuntu.net/blog/lubuntu-1004-now-available-download

here a list from distrowatch: http://distrowatch.com/search.php?category=Old%20computers

- if you pc is a very low resource pc you can try different Linux distribution something like:
 DSL http://www.damnsmalllinux.org/
 Puppy Linux http://www.puppylinux.org/
 Slitaz http://www.slitaz.org/ : Slitaz 3.0 release note http://www.slitaz.org/en/doc/releases/3.0/relnotes.en.html

1.a) Please always prefer to download them using torrent if you can...

1.b) BE ABSOLUTELY SURE to verify the md5sum https://help.ubuntu.com/community/HowToMD5SUM
of the downloaded iso image BEFORE to burn it

1.c) burn it using infrarecorder if you are using Windows at lower speed you can do

1.d) boot your pc from cd and install...

--- 2) please download the 700 mb file http://www.ubuntu.com/desktop/get-ubuntu/download simply press on download button
To avoid download errors download the desired ubuntu iso install cd image using the torrent protocol.

- if you are using Windows please install a torrent client i suggest you http://deluge-torrent.org/
and download the iso using a .torrent link from here:
http://releases.ubuntu.com/10.04.1/ubuntu-10.04.1-desktop-i386.iso.torrent

--- 3) PLEASE BE SURE TO 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/10.04.1/MD5SUMS go to the next steps.

--- 4) burn the iso image onto a cd, to do it install and use http://infrarecorder.org/?page_id=5 burn the cd at lower speed you can do and activate the data verify

--- 5) 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

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

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 "Test Memory" to deeply test your ram healty, if your pc freeze at installation or installation doesn't start.

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

If you get a blank screen at boot after install or booting from the Ubuntu install cd please read:

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

If you have trouble with intel8xxx graphic cards:

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

--- 7) Ubuntu Manual, it's very informative: http://ubuntu-manual.org/
Click on the "download Button" to download the latest PDF version.

The online help https://help.ubuntu.com/10.04/index.html

--- 8) Relax and fun
http://planet.ubuntu.com/ and Full Circle Magazine http://fullcirclemagazine.org/