Hi: My Acer LCD moniter has started its problem two weeks ago, when I turn it on the screen comes a seconds then went off but there is still faint screen you can see. the green botton light in contiuously on. I have changed all 4 capacitors but the same problem stays, so can you guide me to get my screen work again. Thanks Kaka

It also doe the same if you use this monitor to your brother's PC? Just want to make sure since you will have to open up the monitor if the monitor is bad for sure.
It is more likely to have power supply problem due to unstable DC feeding the circuits because of bad DC filter caps as you can see to these ACER monitors here and also ALL other brands as well.
http://s807.photobucket.com/albums/yy352/budm/ACER/

You can learn about troubleshooting here:
Basic LCD monitor and TV troubleshooting guide:
http://www.fixya.com/support/r5093881-lcd_flat_panel_tv_troubleshooting_guide
http://www.fixya.com/support/r6150077-basic_lcd_monitors_troubleshooting
http://www.fixya.com/support/r7406380-tv_training_manuals
Failed TV and Monitors pictures: http://s807.photobucket.com/albums/yy352/budm
Learn about bad caps: http://en.wikipedia.org/wiki/Capacitor_plague
Parts: www.shopjimmy.com
Parts: www.interliquidparts.com
Capacitors kit: http://lcdalternatives.auctivacommerce.com/Default.aspx he can make you a set of caps.
Or www.digikey.com, just make sure to use caps with low ESR, 105c, high ripple current and long life rating such as PANASONIC FM or FC series.

this is because the boot up screen and the welcome screen comprises of many differences they differ in resolution ,colour depth etc so if once the moniter is set for welcome screen it may be irregular for boot window

could be capacitors, are leaky and need resoldering on board, have a quotation with qualified service tech and compare the new price,..but repairing should be cheaper,....

You most likely have a capacitor that has changed value. When a capacitor goes bad it will work after it heats up. Sometimes a bad cap will have a bulging top or show signs of leakage. Sometimes can only be checked with a meter.

first reinstall the xp

This monitor has "back lights" that are essentially like flourescent lights. These are high voltage lights and can easily fail. since you are getting some light initially, I would suspect a defective part that heats up a bit right away and then fails. I would try to replace the entire backlight board. This is the small board on the side (usually).
Dan

there is something that defect on the main board power input.

hi guys, first run the system in safe mode, and with vga mode, see if it is the same problem ?? let me know

This is possibly an inverter. When the monitor goes out, examine the LCD to see if you can see a faint image of the video being displayed. IF so, replace inverter. If not, possibly a bad LCD or video circuitry.