I found an answer here: http://www.tomshardware.co.uk/forum/275037-32-card-ready-boost
apparently Class 4 sdmc cards will work if you have a class 10 there is a hack to make that work, open regedit, START BUTTON Search box at bottom enter REGEDIT then this path...
HKEY_LOCAL-MACHINE, SOFTWARE, Microsoft, Windows NT, current version, EDMgmt
you will see several SDMC cards that begin with ?? (2 question marks) right click on all of these and delete the entries.
restart windows wirh SDMC card in slot now re open regedit and fololow same path
HKEY_LOCAL-MACHINE,SOFTWARE,Microsoft,Windows NT,current version,EDMgmt there will be a new entry at the top of the list with 2 ?, this is your card, select it then select device ststus and change the entry from 1 to 2 close regedit now you have a class 10 card running capable of READYBOOST
apparently Class 4 sdmc cards will work if you have a class 10 there is a hack to make that work, open regedit, START BUTTON Search box at bottom enter REGEDIT then this path...
HKEY_LOCAL-MACHINE, SOFTWARE, Microsoft, Windows NT, current version, EDMgmt
you will see several SDMC cards that begin with ?? (2 question marks) right click on all of these and delete the entries.
restart windows wirh SDMC card in slot now re open regedit and fololow same path
HKEY_LOCAL-MACHINE,SOFTWARE,Microsoft,Windows NT,current version,EDMgmt there will be a new entry at the top of the list with 2 ?, this is your card, select it then select device ststus and change the entry from 1 to 2 close regedit now you have a class 10 card running capable of READYBOOST
Had SCSI instead of SDMC and edited from 12 to 2 instead of 1 to 2, but worked like a charm.