XP not saving screen resolution on reboot

I have just bought a new monitor, a 22" hanns g widescreen with a resolution of 1680 x 1050. It is HDMI so I have connected it to my Nvidia Ti4600 graphics card using a DVI-D to HDMI cable.

I can select the resolution and everything is fine, but whenever I switch the PC on the resolution has been reset back to 1024 x 768. I assumed that once applied, the new resolution would be saved and used at reboot. The annoying thing is that as well as always having to set the resolution, I can't arrange my desktop icons as they all end up crammed back in the middle of the screen after a reboot!

I have done a lot of searching but surprisingly can't find an answer to the problem. Can anyone assist? Is there a way to get XP to boot at 1680 x 1050 or correctly setup for my new monitor?

Thanks.