Kubuntu 11.10 was running well, then got "sticky." I coultn't view videos, although I had a player installed. I tried to install another and kept getting "packagh manager in use by another app." even after reboots. I tried to install Google Chrome browser as it aas a built-in pjaer. Got a message that it could damage my computer, which I foolishly ignored. Then I was no longer able to boot, even from a CD. Finally tried Knoppix, and can now boot from Kub. 11.10 and 12.04 CDs, but despite having run updaet-grup 2-3 times, my second installation of 11.10 and both installations of 12.04 don't show up. All three of these were done after the Google Chrome disaster. I'm running fine from the CDs but can't follow links in emails. The original 11.10 on HD won't run. Do I need to do a low-level format on that partition? More importantly, how can I get the subsequent installations so I can select from grub?

What operating system(s) do you currently have installed?
Are you able to boot any installed system? or only from CD/DVD?
How are you running update-grub? Just running update-grub from the CD won't work. Take a look at the link below, particularly the methods in Section 12 on Reinstalling Grub2:

https://help.ubuntu.com/community/Grub2

If you have problems with any of the methods in the link you try, make note of them and any specific errors and post what exactly you did so someone can give specific help. Also, if you get Kubuntu working and put its Grub2 bootloader in the master boot record, when you subsequently install other operating systems, put the bootloader on the root partition of the new system and reboot Kubuntu and run the sudo update-grub command.