Welcome to GeeksToGo,
My name is Cbarnard I hope I may be of some assistance to you.
Something happen to my old Pentium. The C hard drive is 99% full. I've deleted & uninstalled all that I can. It will not do any thing because not enough space. It is running Win 95. Also, because of this issue, both the D & A drive say drive not ready. Both were working find before this issue.
what is the size of this HDD?
Is this a desktop? if so proceed on...
You have a second computer set up with ubuntu currently
How old is the second computer?
Please if you are confused or don't understand my instructions stop don't go any further, I would rather re explain something in a different way than have a mistake made..
What you can do provided the HDD are the same interface(data connection), and you have enough 4 pin power connectors, pull the HDD you intend to format out of the current tower. Then mount it in the other tower, hook up the power, and the interface cables. Please make a note where the jumpers are located, and what pins they are on. You will need to return them here after we are done. Please set the HDD you intend to be formatted to "Slave" Then set your other HDD to Master with slave present.
Provided those instructions work, You should be able to boot up Ubuntu, and use G parted. It comes as part of the software in Ubuntu. G parted is partition software that will be able to make the hard drive usable again. Open G parted and look for the drive that you want to format. PLEASE
make sure you select the correct drive. The next action will delete everything on the hard drive. Once you have selected the drive to be formatted, specify its file system to be EXT2 or EXT3, then delete\format that drive. You should now be able to remove the slaved drive from that computer and return it to the other computer. Please place the jumper settings back to were they were and proceed with your Linux install.
Good luck and let me know how this worked for you