Macbook Left Click Stopped Working

Hello All.

I realise that this issue has been posted before in some guise or another, but none of the circumstances or solutions have been of any relevance.

I have an old macbook (1.83 Ghz 32-bit core duo), which has recently started playing up.

If I attempt to use the trackpad at all after starting the machine, left click stops working.

When I say it stops working, I mean entirely.

I have a usb mouse plugged in, which works fine unless I touch the trackpad, at which point the usb mouse left click fails as well.

I have seen various potential solutions involving batteries, bluetooth devices etc, yet none of these are pertinent.

I am assuming that the issue is related so software rather than hardware, as if there was a hardware problem, It should not affect the usb mouse.

If needs be, I can perform a reinstall of the OS, but I would rather avoid this if at all possible, so if anybody has any suggestions outside of the ones posted on other forums, I would be very grateful of the help.