i dont know if this is caused by the new sound card or the new monitor. it never happen before. i bought a soundblaster x-fi fataliy pro and a 24" acer last week. i set the desktop resolution to 1920x1080. it just happened 2 days ago. now every time i turn on the pc, my desktop resolution is changed randomly. sometimes 800x600, sometimes 1280x720 and so on. i have to set it back to 1920x1080 every time i turn on my PC. any idea whats wrong? i am using GTX 260 video card.

You have a ghost using your PC when you aren't around. Seriously, it does sound like someone is changing the resolution. Is it possible someone else is using the PC? Games sometimes reset resolutions. If the resolution was falling back to default settings that would be different. Try using a new password for login. If the above is not a viable explanation then try updating the graphics drivers and installing any drivers that came with the monitor. Also, verify the graphics card is fully seated. You are clicking on apply then OK when selecting a new resolution?