Ok, you have several options:
1. See if you currently have the 64 bit version of the recovery disk and reinstall window
2. If you don't, you can get the 64 bit recovery disk from you laptop manufacturer (there could be a fee, ask them for details)
3. Your keys works for 32 bit and 64 bit window 7 given you don't swap the version (starter, home basic, home premium, professional, enterprise and ultimate). You have to figure out the rest.
But if reinstallation is too much, then just use 32 bit. You still get more RAM than you currently have, although the investment diminishes and you have to start asking yourself whether you really need that upgrade or you just want an upgrade.