I'm buying a new laptop and have all the software I ned on my old one. Can I just copy the old C drive to my external hard disc and then transfer it to the new laptop? Will the old programs still work ok?
I would pull the old hard drive from your computer and get a external 2.5 inch case for it and use it as a external drive.All of the programs should work just fine.I even went as far as to put a folder on my desktop labled it "old laptop" and transfered all the files and folders over to that folder.Getting HD out of Laptops is not very hard depending on make and model.Most of them have a seperate access door for them so no major "take down" is necessary.
If you plan to sell the old laptop,,just buy a cheap HD for it from Newegg,Reformat it and install OS and its good to go.
This would only be true if all the applications running on the old system were self contained. However, a lot of applications written for Windows require library files that are in /System32, part of the registry, or embedded under the users directory in a hidden folder called application support. Those files will not be on a clean install of windows, because the application installer puts them there.