You can also duplicate a system drive by cloning it. After that the new disk can be swapped with old. I use the free EaseUS Todo Backup for backups (duh) but it will also clone a system disk.
If you buy a new SSD the manufacturer normally provides a free utility to do the transfer. Since this thread was started, prices have falled dramatically so there’s no excuse for living with a drive that’s too small. I picked up a 1TB SSD for less than 100 bucks in the sales …
The price drops really have been stunning. About a month ago my non-DAW PC totally failed. Shopping for a replacement the price difference between having a 500GB or 1TB SSD was $20. And about 6 months ago I got an additional SSD for sample libraries. It was the same drive that I had previously bought almost exactly one year earlier. Over that time the price had dropped nearly in half.