Have been using WD Smartware on an XP Pro SP3 system with the same issues as everyone else.
Noticed that WDMFE.exe and WDRulesEngine.exe combined will use up 90-100% of the CPU, grinding my machine to a halt. This can last for two hours or so, after which it seems to settle.
I’m using version Smartware version 1.5.16.
A software fix is long overdue WD.