I've managed to emerge triumphantly from a clean Windows re-installation with everything still working. It's a job I hate, but I hadn't done it for several years, and the machine was getting badly cluttered.
I took advantage of the mild day to check the bees. Hive 5, as I expected, is expanding its broodnest merrily, with brood on three frames. The others aren't expanding at all yet; I wouldn't expect them to with no appreciable food supply available yet. Hive 5 was stingy, with bees jumping off the frames. All the more reasoin to requeen it ASAP. The only blessing is that a rapidly expanding colony is likely to have early drones. Once there are a reasonable number I can raise a new queen. She'll be crossmated, but drones come from unfertilised eggs, so they won't be affected, and I can hope for well-mated queens later in the season.