Turning on my macbook- all i see is white screen and 'no' sign

You may need to reset the PRAM.
Start your computer and hold down the option, command (apple), P and R keys simultaneously until you hear the second chime. Then release.

This will reset the perimeter RAM (PRAM) and may allow your system to start, which it will do immediately if it capable.
If this is not the case and you have already tried removing the RAM and the HD, you may need to have the motherboard tested.

The problem in blank white screen is the display (LCD). Send it to a technician for repair. The blinking folder with a question mark is conflict on drivers. Have you installed a software lately? If you do please uninstall it. Maybe that is the cause of having a blank white screen.

Leave the Macbook air turned on until the battery goes dead. Then Connect to power and start it up. That should solve the problem. You problem was caused by not letting an update install in full.

Press the F2 key several times to make sure that the screen brightness is up.
Put your ear down on the laptop on the zone left of the trackpad and below the keyboard and listen for the little whirring and clicking noises of the hard drive. If it is making noises, just walk away for at least 30 minutes and see what happens in that interval.
Look carefully at the screen in good light and make certain that here is no image on it. You could just have a bad backlight.
If so, you can connect the DVI port on the MacBook to a computer monitor or most flatscreen TVs and regain access to the screen until you get the backlight repaired.
You might try that regardless. Even if your display is totally inoperative, the DVI port may still function.
If the drive has stopped making noise and the screen is totally blank, 1. Try starting up the MacBook with the DVD that came with it, and if that doesn't yield anything, 2. Take the MacBook to the Apple Store and ask for a Genius appointment.

that normally happend when the macbook do not find the software you can read this apple post http://support.apple.com/kb/TS1440

Parallels won't have caused this, Bootxchanger might have but it's not likely. More likely is that you HD is faulty.
A largish number of white Macbooks shipped with faulty Seagate HD which, although fine to start with, started failing after about 1 year of use.
I've seen 3 in the last six months.
Thankfully the HDs in these MacBooks can be changed in just a couple of minutes, the bad news is that the data on the drive is generallycompletely destroyed.
Try starting up from your install DVD, but not do the install. After you get asked about language, at the next screen, go up to the menu bar and locate disk first aid. Run that - you may be lucky and it fixes it or you may not.

your hard drive has prolly crashed, same thing happened to my buddies macbook. when he turned it on, it went to a blank screen.  Im sorry  but hopefully you still have a warranty on it bc it was 300 $ for a new hard drive that my buddy got.  take it in to apple and have them look at it.

Sounds like it could be a corrupted OS; have you tried forcing it to start up with the OS disk, holding down the 'C' key? That's the first place to start...

If it won't start up like that, you probably have a hardware problem. (You can get excellent troubleshooting guidance at: http://www.ifixit.com/Guide/Mac/ ) depending on your level of geekness, and assuming the warranty is expired?

Good luck
dennismacfreak

Itunes is very tricky and its freezes computers very badly.try to take out battery and than turn on computer slowly,Soon if you can you need to reinstall itunes maybe to start to work better.
Good luck!

My computer used to do the same thing, I found out it was my motherboard / logic board and a hardrive combination. end cost $1500..so i bought a new Laptop. Go and get those things tested.