Screen is black on my acer aspire one

Well this depends on what model you have. First make sure it is plugged in and the battery is charged, then try turning it on. If this doesn't fix the problem, you may need to update your bios. Acer provides very detailed instructions on this here: http://netbooks-us.custhelp.com/app/answers/detail/a_id/66/session/L3NpZC9YS2pVZEZLag%3D%3D/sno/0

You need:

• A working USB thumbdrive you can erase. I used an old 64meg.
• UNetbootin. Download from here: http://unetbootin.sourceforge.net/
• The files to flash the BIOS. I used the most recent version from here: http://sites.google.com/site/maclesblogspotcom/

Download all the files to an easy to find location.
Steps to prepare the USB drive:

• Format the USB drive using the FAT file system, not FAT32.
• Start UNetbootin and choose FreeDOS as the distribution. Screenshot here.
• Unzip the BIOS files and copy them to the USB drive
• Make a copy of the BIOS file and rename it as ZG5IA32.FD (this appears to be very important – my reflash failed until I did the copy & rename)

Reflash the BIOS:

• Make sure the AAO is turned off, the battery is attached and the power adaptor is plugged in.
• Insert the USB drive
• Press and hold FN + ESC and press the power button to turn it on. Release the Fn & ESC keys. The LED in the power button will flash.
• Press the power button again once and wait. Mine took ~3 minutes, but I’d advise that you let it sit there for at least 5 minutes just in case your’s takes longer.

When the reflashing is done, the AAO will reboot and, hopefully, you’ll be back to normal.
If it doesn’t work, try reflashing again. The keypress sequence is a little tricky.
If the second try doesn’t work, then you’ll probably have to send it off for repair.