In case anyone is still interested in this topic, I just managed to install RootsMagic4 on Ubuntu Linux v9.04 using WINE (software which creates a kind of virtual Windows environment inside Linux)
Everything seems to be working normally, but I'll report back if I hit any problems.
After playing around with it on my laptop (dual boot with XP), I decided to switch fully to Linux on my PC after a fatal Windows XP crash . . . though I'll probably have another go at reviving XP once I get Ubuntu set up to my liking, 'cos I don't like being beaten by a stupid machine . . .

Mike.