My screen resolution went to low on it's own. when i reset and restarted, nothing had changed. windows vista?

i was on Twitter when it happened. i had just posted a tiny url and everything went jumbo-sized! i went to "display settings", it showed as "highest". i also checked dfi settings and it said they were at the standard 94.so i reset both and restarted the computer. font is still oversized, yahoo mail says "resolution too low for best results". help!