I have an E-Machine W3107 desk top. I recently installed a western digital 120 hard drive as a slave but it would not jump. Can you give me any help in getting my system to jump. Thank you.

I'm sorry I'm not sure what you mean by "jump". If you mean to be recognized as slave & you already have a master hdd make sure you have jumpers on both hdd's set; master as master and slave as slave. Using cabel select requires (I could stand to be corrected) one hdd cable with at least 2 drive connections on it, and you would want your 2nd (slave) drives jumper set as CS.
Then it's best to boot into the bios and see if and what the drives are being recongnized as. Sometimes it helps to set the second one (maybe both) on Auto. If still not recongnized try the 2nd drive setting on User.
I hope this pertains to your promblem as I'm not sure what "jump" means. If not, please detail your problem further and I will
try another alternative.

Jump? Ha! Never heard that term. How about boot?
Nowadays people just load drives as Cable Select; it should have worked with the old drive set to Master, but try to set them both to that and try again, or boot to a LiveCD or the drive utility disk so you can configure them on that. If they don't appear correctly in the BIOS, just double-check that power and data cables go to each drive, etc. You may need to follow the BIOS instructions or enter the BIOS controls by hitting DEL or F10 on powering up until the menu appears; then you can select the drive to try to boot first, etc. and save your settings.