keyboard problem!!!!

I have been using Logitech Wireless Keyboard and Mouse combo (more than 3 years), recently, the scrollable content if any on the screen keeps scrolling down. I tried switching off the mouse & connected another USB mouse but still the problem happened, after I removed the wireless receiver & now...

Some keys in my Dell Desktop Keyboard can be pressed only if I press it from the center of the key. Pressing elsewhere on the key is little harder.

Yesterday I bought a new Keyboard for my PC but the problem i'am facing is that the left "shift" key is giving errors while typing. Holding the left "shift" key gives "|" and sometimes "\". for e.g, if i have to type "@" it gives "|@" or "\@". is there any fault in the keyboard or is it a driver...