Hello!
I downloaded ReactOS-0.3.15-REL-vbox.zip from the site and ran it in
VirtualBox 4.2.16 in Windows Server 2008 R2.
See my report with 4 problems I experienced. Three of them are
serious. Hope this message will help you improve ReactOS.
== Problem 1 ==
Menu Machine->Add failed with "Failed to open "C:/Program
Files/Oracle/VirtualBox/VBoxGuestAdditions.iso"".
So I went to ReactOS.vbox and removed these lines:
<DVDImages>
<Image uuid="{38b58d16-ded5-4c11-997d-66b88780fbb1}"
location="C:/Users/Z98/workspace/reactos/ReactOS-BootCD.iso"/>
<Image uuid="{39d01696-2de6-4272-8bc8-0cc8836273ca}"
location="C:/Program Files/Oracle/VirtualBox/VBoxGuestAdditions.iso"/>
</DVDImages>
(I didn't have either path on my computer.)
After that I managed to add the machine.
== Problem 2 ==
The first boot failed with blue screen 0x1E (0xC0000005,,).
Going to Settings and disabling the USB controller fixed this. I could
finally boot into the system.
== Problem 3 ==
I did Start->Reboot in the start menu a number of times. About half
the times boot failed with blue screens 0x1E (0x80000003,,) or 0x7E
(0x80000003,,).
== Problem 4 ==
After shutting down and powering the machine on boot process failed
with blue screen 0x44 a couple of times
I saved screenshots of those BSODs. Will send them if you are
interested. (And I hope you are.)