This driver comes with Windows 7, but it allows a maximium of 1024x768 resolution. How could I increase this value to 1280x800? Is it posible to modify - hack - tweak - recompile this driver? The manufacturer does not provide a proper driver.
It can't be done. The VESA interface works by assigning modes integer identifiers, not by specifying the X and Y resolution. There is simply no integer you can specify that corresponds to 1280x800 in your graphics card's implementation. (Otherwise, you would be able to select it because the default VGA driver would detect it.)
Windows 7 typically detects your monitor and assign a maximum of whatever the monitor can support. Unless your video card is super old, as in PCI or AGP 1024 by 768 is definitely not a upper limit of any modern video card. Even AGP devices did better than that. Your monitor is more likely to be the issue. What is your monitor make and model?
In addition, if the Device Manager actually says "Standard VGA Graphics" that means you have not install any video card drivers and that issue has to be resolved first. Since, I have no idea what your video card is I suggest Slimdrivers. SlimDrivers
This will, in most cases, display a list of all out-of-date drivers and offer you a link to download the newest ones. Please install all drivers first.