Screen resolution changed after forced restart

Yesterday i was on Facebook for the first time and i came across a video and tried to play it. I was then told i didnt have the latest Flash Player 9 installed. I clicked on the link to install it and it installed no worries. All of a sudden, shortly after, all the windows/programs i had open started closing down by themselves (as if i had clicked on restart or shut down) and the computer restarted itself. I read later in the system "event viewer" that:

The Windows Installer initiated a system restart to complete or continue the configuration of 'Adobe Flash Player 9 ActiveX'..

Anyway, after the restart had been performed, i realised that my screen resolution had changed. I opened Display properties to change it back to the previous setting (1440x900) but that resolution wasnt available.

What i would like to know is has anyone else experienced this problem and is there any way of creating a custom screen resolution?

My graphics card is ATI Radeon 9250 128mb
My monitor is Acer AL1916W (widescreen)
My OS is Windows XP Home SP2