Q: Can I use my iMac display with my Power Book

The PowerBook has been discontinued for years. Do you mean a MacBook Pro?

Target Display mode only works on a 2009 or later iMac. If you have one that's so old the max RAM is 2GB, it's not going to support TDM.

An iMac which has a RAM limit of 2GB is too old for Target Display mode, but you can use a product such as ScreenRecycler over a network.

(135194)

2 things:

1. PowerBooks have not been made since 2006 when they were discontinued. Perhaps you meant a "MacBook" (very different to a Powerbook)?

2. Depends on exactly how old the iMac is. Here are the requirements:

Use your iMac as a display with Target Display Mode - Apple Support

However if it only supports 2GB Ram its very likely too old.

Guess I took too long to answer.