I have 3 acer al1603w widescreen monitor.. it was

hi,I had same kind of problem I was using CRT monitor with xp OS and due to some problem i thought to change it to LCD so i bought this acer monitor and start working with it later some days i planed to upgrade my system so when i was reinstalling OS i got the message input not supported so I checked with vendor carrying my monitor the reason for this problem is, model does not support dos mode so i connected with CRT monitor and reinstalled OS and set the settings to 1024 to 768 and reconnected with LCD it started working.try this it worked for me

Sounds like somebody messed with the monitor setup on the monitor controls. Check the manual to set it up correctly. If they changed the monitor's Frequency settings, the problems you are having will occur. Gotta set them back to 70Hz and check the other settings. If you need a manual, get back to me with the exact model number of the monitor.