So you have Windows 7 and Windows 8 installed to dual boot? Is that what the title of your post means?
Regardless - please provide the other specs of your laptop, or at least the full model number so we can look those up. And where do you mean "available" - do you mean that's what shows as Free Physical Memory in the task manager? Or that's what shows in the system info box? Provide either a screenshot or detailed description of exactly where this information is showing.