Virtual PC 2007 DR7 Trick

//http://waleedassar.blogspot.com
//http://www.twitter.com/waleedassar
//Use this code to detect if Windows XP is running inside Virtual PC 2007
#include "stdafx.h"
#include "windows.h"
#include "stdio.h"
#define CONTEXT_ALL 0x1003F
unsigned char ARR[4]={0};
unsigned char LIST[28]={0x39,0x3a,0x3b,0x3c,0x3d,0x3e,0x3f,0x40,0x41,0x42,0x43,0x44,0x45,0x46,0x47,0x48,0x49,0x4a,0x4b,0x4c,0x4d,0x4e,0x4f,0x50,0x51,0x52,0x53,0x54};
unsigned long current=0;
unsigned long hits=0;

int __cdecl Handler(EXCEPTION_RECORD* pRec,void* est,unsigned char* pContext,void* disp)
{
    if(pRec->ExceptionCode==0xC0000096)  //Privileged instruction
    {
        *(unsigned long*)(pContext)=CONTEXT_ALL;
        *(unsigned long*)(pContext+0x4)=(unsigned long)(&ARR[0]);
        *(unsigned long*)(pContext+0x8)=0;
        *(unsigned long*)(pContext+0xC)=0;
        *(unsigned long*)(pContext+0x10)=0;
        *(unsigned long*)(pContext+0x14)=0;
        unsigned long dr7_=0x050001;
        unsigned char* pDr7_FLags=((unsigned char*)(&dr7_))+1;
        *pDr7_FLags=LIST[current];
        *(unsigned long*)(pContext+0x18)=dr7_;
        (*(unsigned long*)(pContext+0xB8))++;
        return ExceptionContinueExecution;
    }
    else if(pRec->ExceptionCode==EXCEPTION_SINGLE_STEP)
    {
        unsigned long dr77=*(unsigned long*)(pContext+0x18);
        hits++;
        return ExceptionContinueExecution;
    }
    return ExceptionContinueSearch;
}
int main()
{
    for(current=0;current<28;current++)
    {
        __asm
        {
           push offset Handler
           push dword ptr fs:[0x0]
           mov dword ptr fs:[0x0],esp
           STI; Triggers an exception(privileged instruction)
        }
        __asm
        {
            mov edi,offset ARR
            mov ecx,0x4
            xor eax,eax
            inc eax
            mov byte ptr[edi],0xCE
            pop dword ptr fs:[0x0]
            pop ebx
        }
    }
    if(hits!=28)
    {
        printf("Virtual PC 2007 detected\r\n");
        MessageBox(0,"Virtual PC 2007 detected\r\n","waliedassar",0);
    }
    else
    {
        MessageBox(0,"Expected behavior","waliedassar",0);
    }
    return 0;
}