Maptech would be a good choice. I use it on an old Dell laptop (266MHz) and it works well. I use the ‘free’ version (which doesn’t do the tides) and have a collection of chart CDs I’ve built up over the years. The recent repackaging by Maptech makes the charts a particularly good buy now, though – £99 for the whole UK or similar for Elbe to Gibraltar. The main advantage to me is that they are Admiralty (or equivalent French, German etc. charts) and much more ‘user friendly’ than vector charts (although these are getting better).
I use a Garmin 128 GPS into a serial input but I think new laptops only have USB. I would therefore recommend one of the latest USB GPSs. I also have one of these with my ‘new’ laptop which serves as a backup to my system if needed.
I also have recently acquired a Dell handheld with Bluetooth and bought the GlobalSat bluetooth GPS which works a treat sat on the chart table while I use the Maptech charts through Memory Map software upstairs on the Dell for detailed pilotage.
Don’t you just love the toys!