unfortunately retail versions are for one licience (single user ) a full version can be used on one machine at a time only , if you install it on a new PC you will have to uninstall it on the other. ,otherwise the activation key will get flagged when you activate it and soon after both machines will become de-activated . its a difficult system to understand but its there to stop piracy .If you buy a full retail version you will have both 32bit and 64bit discs and you can use either with the same key ,but not at the same time and not on more than one machine .
so ,taking that into account ,you have a choice ,you will have a grace period on the new computer (30days) during that time you can use it without activating and your laptop will stay legally activated . you will need to remove it from your laptop once you activate it on the new PC ,and there is every chance that the new activation will fail as microsoft will know its on a different machine than it was registered to.
dont worry ,during activation you simply use the option to contact microsoft and explain that you have uninstalled it from your old PC and put it on your new one . remember the PCs must both be yours .(non transferable) . if activation fails you will have very limited access to your PC until you sort out the activation.
it sounds daunting ,but its not that much bother really .