virtualbox.org

Hello everyone firstly,
I try to install fedora on VirtualBox 4.2 in Windows 7 64 bit. I downloaded Fedora-17-i686-Live-Desktop.iso and then start to installation.Everything go right until installation was complete.When i try the reboot fedora ,virtualbox stopped.
This isn't my first guest os experience on virtualbox.I used ubuntu before a few months,just the version of virtualbox was different.I don't understand this problem.
Can anybody help me to solve the problem?

Post the VM log file as a zipped attachment. The VM log file is called "VBox.log", and can be found in the "Logs" subfolder of your VM folder.

After my problem I removed my Fedora guest os,after I try to install ubuntu. It has same problem too.Log file is in attachement

I see no crash in this log. Indeed the VM appears to have run normally for 50 minutes - at which point you grabbed the log (in future please shut down the VM, then grab the log).

General observations however: you have only provided 512MB to the VM, which may be a problem, if it doesn't meet the min RAM requirement of the OS. Also a problem is that your host only had 768MB free when the VM started, meaning that even 512MB is using too high a fraction of host RAM IMHO. Finally, many modern OS's require you to turn on the "IO APIC" feature.