How do I change screen resolution on primary OS from a secondary OS?

[10ftcoke]

I recently got a radeon hd 5570 and whenever I change the screen resolution from 1440x900, it says input not detected but then it changes back after 15 secs. However one time I tried changing screen resolution from the notification area and this did not allow for the 15s safety readjust so I was stuck with input not detected. I tried rebooting many times, no luck.
Then I went in safe mode but it won't allow me to go up to 1440x900 because safe mode doesn't load my gpu drivers needed so it defaults to trash onboard graphics. now this is all on my windows 7 64 bit

I have windows xp installed on the same hd different partition and the only resolution that works is 1440 x 900.
So the question is how can I change the settings on my windows 7 system files so screen resolution becomes 1440 x 900 while I'm booted onto windows xp? or is there anything else I can do from safe mode?

 

[SinisterSalad]

The easiest thing to do is hit F8 after the BIOS post to get the startup options. You should have a choice to enable VGA mode. That will boot normally into Windows in 800x600, which will have your drivers enabled, giving you a chance to play with your settings. It's possible that the refresh rate is set too high on the 1440 setting, or your monitor just doesn't happen to support that size.

 

[10ftcoke]

I can already get 800x600 through safe mode. My BIOS doesn't have a F8 option either. its phoenix i believe from 2003. my options are esc for boot menu f1 for setup and f10 for system recovery, although system recovery doesn't do jack

 

[SinisterSalad]

The F8 function is a Windows function, it should be an option on the same screen as selecting safe mode, where you start tapping F8 before the windows logo comes up.