You should uninstall previous drivers before installing new ones.
A good program to ensure you've removed all files is "Driver Cleaner Pro" which is free to download & use.
If you want the best way to install your drivers then...
1) Boot into safe mode
2) Use Driver Cleaner Pro to uninstall drivers
3) Restart computer (Boot normally into Windows)
4) Install new drivers
5) Restart when prompted
6) Done
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