Upgrading from integrated graphics chips can be tricky. Windows does not make it easy.
There is a very strict method involved in doing this.
1) With the system booted to the Windows desktop. Remove the existing onboard video drivers.
2) When the system asks to restart, do not allow it to reboot. If you do reboot, start over.
3) With the system powered down, install the new video. Do not connect your monitor to it yet.
4) Power up, and get into the system BIOS setup. If you fail here, you need to pull the card back out and start over.
5) Once in the system BIOS, find the option to disable the onboard video chip. If there is not one, you are pretty much stuck with the integrated chip. If there is, then disable it.
6) Power down the computer and connect the video monitor to the new video card.
7) Now power up and continue to the Windows desktop. It should look pretty ugly.
8) Install the new video card drivers from the CD/DVD that came with the card. (Update them, if you want, after you install the original drivers).
That should do it, if the new card is working correctly and you could disable the onboard one.