virtualbox

hi, i am using window 7 in virtualbox 5.1 but some error come on my window 7 means firstly it become vdi (normal,inaccessible) when i solved this inaccessibility that is biggest and huge error and when i open my window as normal so it occur window repair erro when i click on window repair it...

i was looking at Microsoft's Community about XP emulator installation on Windows 7 and I saw a plug for "Virtualbox" that looked interesting, but I've never heard of it. What's the best route? .....in your humble opinions; thanks!!!!!!