Was away for 10 weeks last year and took
one of these.
Probably not a current model but may be a few around at discount price. Brilliant - A5 footprint, wifi, XP Pro. Don't buy a case for a portable pc - too bulky and expensive; get some bubblewrap and make a double-thickness "envelope" to slip the pc into, using parcel tape to hold it together. I'm still using the one I made 14 months ago....... Take a plug-in USB2 hard disk for backup, or probably better, one of the newer high capacity "thumbdrives".
If you use internet cafes, keyboard loggers and security can be a problem so if you don't take a portable, a thumbdrive with portable email client and browser is useful (the keyloggers might get your passwords, but if the application isn't there, they can't do much).
PortableApps works very well.
If you take the pc, get a Skype account and USB skype handset - save a fortune by phoning from the zillions of wi-fi hotspots at filling stations, cafes, bars, hotels and definitely NOT (oh no, definitely not

) from any unsecured wifi connexions you might find in cities, for instance......
Don't pack the pc against the plastic or metal of your panniers or topbox. Gets too hot.
Good luck and enjoy.