laptop boots but no keyboard or mouse

Acer 5100 will boot to a new XP install which it did mostly on it's own as I cannot use keyboard or mouse. (Not sure if this matters or not but this is a used hd with a gateway install on it not acer)I cant reload anything from the cd as I need to push a button too. I tried a usb mouse instead of the pad on the machine but no use. I even unsoldered the cmos battery for a day and place back in to try to reset the bios, nope. One other thing is on occasion when it boots I get no video. So I have to hold the power button down to shut off and try again whatever the problem is. . Can't access the bios that wants F2 button. Any ideas on this would be helpfull

Try another keyboard, use a PS/2 keyboard. The reason the mouse didn't work was probably because support for it wasn't turned on in the BIOS.

No harddrive from another computer will boot any computer.

well, I guess I have another problem...no ps/2 port. I forgot to mention that. I did try a wireless usb mouse and keyboard and I did try a usb corded mouse but no help. I don't have a usb corded keyboard. Even after it boots up to OS the usb mouse has no connection. Makes me think that maybe a usb keyboard may be ineffective too.

Did you use a usb keyboard before?

Actually I bought this unit from a person that was having hd problems with it they took the old drive and I thought I could fix it by putting in a new one. So I am not sure. I think not though. I did replace the keyboard with another from a same model that was working.

Odds are the keyboard drivers and USB drivers have gone missing.

ditto what jdc said. But without a keyboard and mouse you can't even install drivers.

So does that mean there is no hope on this issue? I thought there was always a way in...somewhow, somewhere.:(

Does anything else plugged into the USB ports work? You could try a USB wired keyboard, but if that doesn't work, there isn't much you can do at this point.

Can you access the BIOS and use the keyboard? Can you boot using a Windows CD and perform a repair install?

This post and my laptop are still doing nothing! I would like to try to rekindle both here if there is anyone wanting to take this on.
Is the keyboard typically run from the moment the power is turned on through bios or setup? Then maybe the bios is bad...no? Yes? Maybe?

There really isn't much you do at this point. No keyboard, means no access to the BIOS to change anything and you can't type or use F keys without one.

If you can't access the BIOS with the built-in or an external PS/2 or USB keyboard, then the main board has serious hardware problems.

I have the exact same problem with the exact same machine. I have also tried everything that was described here with no succes. The usb ports and optical drive are not functioning at all either. I am almost positive the mobo has a serious issue. I will keep you posted on what I discover.