Lost charger can i charge the digital ixus 40 on the computer

Probably not, USB does not provide enough current to charge this type of battery, ergo Canon does not support USB charging. You can buy a third party charger and battery set for not very much and keep this camera working.

No. The camera does not contain any charging circuitry. Please use the supplied CB-2LV or CB-2LVE charger.

You can find a new charger by searching for your camera's model number (add the word "charger") on Amazon, but it might be better to get one of the "universal" chargers instead. There are several makes of these, that will charge any of the small lithium batteries used in cameras and phones, so you won't have this problem again. And the universal chargers are often cheaper than the ones dedicated to a single battery type.

If your camera came with a charger for the battery, then it is unlikely that it will charge from the USB lead.

You have to have a charger to charge this camera's battery.

I found a charger for this camera by searching Amazon for "IXUS 860 IS charger". There are also "Universal" chargers available cheaply that can charge any phone or camera battery, lithium or NiMH.

You can't. The camera does not include any charging circuitry. You have to use the supplied battery charger or a replacement.

Take the battery out of the camera, put it into the supplied charger, and plug the charger into a wall outlet.

you need the wall socket charger

No it won't charge through the USB port. Just buy a new generic charger for the NB-4L battery. They're very inexpensive. Here's some from Amazon:

http://www.amazon.com/s/qid=1217627331/ref=sr_st?keywords=nb-4l+charger&rs=172282&page=1&rh=n%3A172282%2Ck%3Anb-4l+charger&sort=price

I have a canon camera but it's not the same model. Mine doesn't charge while plugged into the computer.

Your manual should tell you this. I think most do not charge this way.