WerFault.exe is a process handling Windows Problem Reporting feature. Sometimes it may drive you crazy because it can lock your files, while you (or a KDE app) want to rename or remove. For me this was the case with files of KMail's MailDir storage.
If you're developer, you'll most obviously encounter many crashes with your developed applications. On any crash, annoying popup appears and says "This program has stopped responding" they it says something about Windows will try to find a solution and fix it. Of course this is a joke, so it is good to disable Windows Problem Reporting. On Vista: open the Control Panel, open the Problem Reports & Solutions applet, wnder the Advanced option you can disable problem reporting. For XP or Windows 2003, read here.