First you must uninstall the old drivers. Try using the method below.
Uninstalling NVIDIA Drivers
The following is an excerpt from a tutorial at EVGA Forums
Uninstalling our current Nvidia driver is quite simple and straight forward (at least something is easy)
Simply go to START, Control Panel and click on "Programs and Features" (then allow the list to populate)
Scroll down to the "N" entries and you will find a section that all start with "Nvidia"
Dont panic if you see more Nvidia listings than shown in the screenshot. This is completly normal, as you may have previously installed other Nvidia driver components. You may see such extra listings as the Nvidia HD audio, Nvidia Update, Nvidia 3D Stereoscopic driver, Nvidia 3D controller and Nvidia Control panel... Ect.
*Important note: Users of older motherboards with Nvidia chipsets may see Nvidia listings that are unreleated to the Display Drivers. Before proceeding as noted below, you MUST know what the chipset listings are, and AVOID uninstalling them. If you uninstall Nvidia Chipset drivers, your system could become non functional and require a OS reinstall.
Now, one at a time.. highlight every Nvidia entry (except the Graphics Driver!!!!) and click "uninstall"... wait till each one is done and says its finished, before proceeding to the next listed entry. Do -ALL- of them until nothing is left but the "Graphics Driver" (with some older drivers it may list "Display Driver" instead...)
EDIT*Important note: If while uninstalling Nvidia display components, the system asks for a RESTART after uninstalling any component (except the Graphics Display) and it wont let you proceed when choosing "restart later", then its OK go ahead and restart and pick up in the Control Panel/Programs and Features where you left off. (thanks to user jdookie for pointing this issue out)
-> -> DO NOT UNINSTALL THE "GRAPHICS DRIVER" entry, untill ALL other entries have been done FIRST <- <-
**this is where alot of users make a mistake, by failing to completly uninstall/remove all the other Nvidia entries before they uninstall the Graphics/Display Driver. Dont make a mistake here, or after your all done installing the new driver... you will have to come back and do it all over again.
OK, there are no Nvidia entries left on the list except for the "graphics driver".
Highlight it, and choose Uninstall The system will ask for a RESTART, you should now do so!!