Dimension 5100, USB keyboard

@vanhud Can you enter the BIOS by hitting the F2 key? If you can enter the BIOS, does the keyboard work and allow you to navigate around the BIOS? Have you tried plugging the keyboard into a different USB port? I am not sure what you mean when you state the keyboard does not work yet you state that the Enter key works. 

I have plugged keyboard into all usb ports. When I turn on the desktop, the black screen comes up and states "Type the system password and press

Enter password:". I try to type password, but no asterisks comes up for my password, only blank and beep sounds. When I hit the enter button, it will state on black screen "incorrect password", which is because I can't type my password. When the keyboard works, the asterisks will show up when typing my password, then I hit enter and takes me to my blue Windows screen to type my other password. When I hit any key, besides enter, it doesn't work and makes beep sound. I have hit the F2 key,  which makes beep sound, and it still takes me to black screen to enter system password. There are buttons on the monitor, and a small screen comes up above the black screen, which I looked through, but didn't seem helpful.

I don't know if it has ever been replaced, got it from someonelse. I read an article stating about steps on taking the coin cell battery out, then putting it back in. If I get a new battery, will that affect what I have saved on my computer? Or if I take it out and put it back in, will it affect what I have saved?

@vanhud If you have never replaced the coin-cell battery (3-volt CR-2032 lithium coin cell) I suggest you start with putting in a new battery. I don't know if that is your problem, but given the age of the PC I would start with doing that. I don't see a procedure in the Service Manual but its location is pictured on the motherboard diagram.

@vanhud Removing and replacing the coin cell battery will not affect what you have saved on your computer's hard drive. The only information you will lose is your BIOS settings, which will likely return to its default settings. If you can enter the BIOS I would recommend that you write down those settings but it appears that you cannot do that. BIOS setting options are listed in the Service Manual under System Setup Options.

There is a password disable jumper on the motherboard. changing Battery DOES NOT clear passwords which is why there is an RTC jumper and a PASSWD jumper.  Given the age of this unit however it will need a new DL2032 battery.

https://www.amazon.com/Fresh-Duracell-DL2032-Lithium-Batteries/dp/B016KQYM8I/

USB keyboard should go into the back below where the Ethernet port is.

https://downloads.dell.com/manuals/all-products/esuprt_desktop/esuprt_dimension_desktops/dimension-5100_service%20manual_en-us.pdf

Disconnect hard drive and turn on.

If its a BIOS password it will still ask for one.

If its NOT a bios password what is happening is that a 16 year old hard drive is crashing at the user login screen.

Disconnecting the Hard drive should allow you to F2 bios setup.

@Vic384 I got a new battery, but it didn't change anything. Me accidentally taking the password jumper plug off made the keyboard work. I have dust in my computer, and saw a clump of dust on the password jumper. I cleaned the jumper and accidentally took the plug off. I put the plug on as it was before, then decided to turn on computer, black screen came up with "floppy diskette seek failure", continued to blue Windows screen to type password, now I can get into Windows. Ha. After getting into Windows, a small screen came up of "format A" and "disk and drive to connect". I did research on the floppy diskette and format A to solve it. I rebooted, F2 to BIOS to turn off diskette drive. I don't have a password to type on the black screen in the beginning of rebooting like it did before, which has to be from taking jumper plug off, then putting back on. That doesn't matter to me.

@vanhud Removing and replacing the PSWD jumper cleared the password, but that does not explain why the keyboard did not work. It is still likely that replacing the coin cell battery with a new one fixed the keyboard problem and removing and replacing the PSWD jumper cleared the requirement for entering a password. You did not indicate at the beginning that you got this computer from someone else so I assumed that you had been using this computer and the keyboard problem was something new, but it now appears that is not the case.

@Vic384 The new battery didn't fix anything. At first I changed to a new battery only, the keyboard still never worked. Then when I accidentally took the jumper plug off from cleaning it, keyboard was fixed. I did later put the old battery in, and the keyboard was still working. So, taking the jumper plug out did something or maybe cleaning the dust on it did something or a mix. Who knows. The password jumper cleared the rebooting password, I still have to type a windows password. The keyboard problem is new. It wasn't a problem with past owner, and I have been using the desktop with no problems, then one day, recently, keyboard didn't work. So, I don't know if past owner everchanged battery, but the keyboard was never a problem for that person or for me, until recently.