Problems mounting a Windows 7 HDD to a Windows 8 laptop.

I just bought a used laptop running windows 8 and was wanting to swap the hard drive for my old windows 7 hdd. Id like to keep win8 but I just need to transfer my old stuff to a flash. After installing I get the "no master boot record found" or something similar. I understand that its the firmware unable to read the MBR due to it being win7. Is there anyway around this or is this laptop just built for win8 and is unable to read from the old hdd at all?

hello and welcome to eightfourms ,its always been a issue to try and add a different hdd to new hardware with out doing a fresh install of windows ,,you say you want to transfer you old stuff to a flash drive ,I think you are going to have to use a external adapter or case for you win7 drive[and hook it to your new laptop via usb port] so it doesn't go through the boot where it needs to see a mbr ,its also likely caused by the new laptop having a uefi bios .and secure boot ect ect

you would be best served by one of these. good luck
Vantec NexStar TX 2.5" SATA to USB 2.0 External Hard Drive/SSD Enclosure - Model NST-210S2-BK - Newegg.ca

or one of these .
http://www.amazon.com/Drive-Adapter-Converter-Optical-External/dp/B002OV1VJW