I'm trying to reinstall Win 95 on my old gateway because it seems to have just dissapeared when I turn the computer on it says please insert valid system disk I get most of the to the instilation and it says line 20 open at adress I have no idea whats going on

"I get most of the to the instilation and it says line 20" I have no idea what that means. But before doing much else, check the CMOS to see if the HD type is correct. Is there a floppy in the drive? If at first you don't succeed, you're about average. M2

Your Motherboard battery may be dead. As stated above, check the settings. A clue as to the battery will be the wrong date & time. Dead battary causes settings to revert to factory settings.

What happened was when the computer was booting up a message apeared that said "insert valid system disk"So I put in the floppy that came with the computer called "System disk" then a menu appeared that had numbers one through four on iit and I pressed one because it said download operating system.then a message came up that said "insert cd with windows 95 or ms-dos" so I did and then another message came up that said "cannot load Line 20 open at adress E3E:2AA"does anyone know what I should do?

Have you checked that the hard drive is recognised by the BIOS ??

Check the first screen that comes up when you power on. It should have a line that tells you what keyboard key(s) to hit to enter the bios. Then look for a screen, normally the first that indicates the drives that have been detected. Do yourself a favor BACKUP!

Yes it does recognize the HD's it says it on the screen I already checked that.