Have you ever heard about using a pen drive as a RAM ?
YES it's TRUE.
Windows 7 is having an option named "readyboost".
by clicking on properties of a pen drive you can find this option.
select use this device and click apply.
okay..... it's done ! your pen drive will ran as a ram. so if you wanted to upgrade your ram just do this with free of cost. :)
if it's not working just format your pen drive as a different file format like exFAT file system.
so enjoy.... have a nice day.