Just passed A+ OS with a low score, 566..... my test was a hard one.... it asked a lot about Windows NT.... DOS command.... HOT KEYS etc.... some very tricky questions, and some questions actually have more than one correct answers...

Over 30 questions are really "questions" and I promise you won't face them in real life!!
As I have 8 years of OS experience, I didn't study much for the exam, one week on OS part of Meyers Passport book, and one cert21 practice exam only.
I don't recommand the OS part of Meyers Passport book. I haven't tried another book but the meyers one really lacks a lot of contents required.
If you don't have much experience on OS, the best is "get an extra computer and try from Windows 95 to Windows XP Pro"!!! 1 hour of playing the OSs is better than 3 hours of study!!
What's next? Network+? or Security+??