Dell keyboard typing funny characters

Try this :
http://www.wikihow.com/Fix-a-Keyboard-That-Has-the-Wrong-Characters

Turn the system off, unplug the ac adapter and remove the battery, now press and hold the power button for at least 30 seconds, plug the ac adapter back in and power it back on. I have seen this fix keyboards issues in many older Dell laptops.

Try the suggested solutions.

If still no cure determine if its a hardware or software issue.
You could run a live CD like Knoppix and test. If there is no problem while running Knoppix its likely to be a software driver issue.

If the problem also persists in Knoppix its a hardware issue.
You will need to replace the keyboard of your machine.

There are many people who are selling the keyboard for you machine.
By a new keyboard if you plan to keep the machine for a while more.
You can get keyboards http://www.nextag.com/dell-latitude-keyboard-c640/products-html or try the ebay. You may find you get better deals at ebay.

Also some info on how to remove the keyboard if necessary.
Replacing the keyboard is an easy procedure. Most DIY enthusiast
should be able to replace it.

Check out the detailed procedure of removal of the keyboard at
http://support.dell.com/support/edocs/systems/latc640/sm_en/keyboard.htm

A new keyboard on sale at ebay
http://www.ebay.com/itm/New-Keyboard-Dell-Latitude-C510-C540-C600-C610-C640-/180582953197?pt=PCA_Mice_Trackballs&hash=item2a0b9530ed

since you replaced the keyboard - and still have the problem ; AND it does not happen with USB keyboard,
i suspect a bad mother board (keyboard controller)
options :
use the USB keyboard , and continue using it
replace motherboard

long shot : you can also clean out the motherboard with a brush and a acan of compressed air (something can be shortin)

I agree with Nobus. Keyboard controller issues.
Perhaps a flexible usb  keyboard can be used as it doesn' take up much room and is easily transported.
http://www.fentek-ind.com/kbmflusbps2b.htm

@ Asidu.....i have already replaced the keyboard but no luck....I can try Knoppix and check can you send me instructions on where to buy/download it and how to run it.

@ Nobus.....i am thinking the same here........but have a question......is the keyboard controller different when I use the USB keyboard....(since the USB keybd works fine)

You can get knoppix from
http://archive.cs.stedwards.edu/knoppix/KNOPPIX_V6.4.4CD-2011-01-30-EN.iso

Down load and burn it on to a CD.

Just thinking did you replace the set with a new keyboard?
If yes make sure you re-connected the ribbon cable properly again.

sure it is different; the inbuilt has parallel connection, when the usb one works like an USB device

found solution on the internet by googling for registry entry issues