during osx installation you need to restart your computer error is showing in my mac book 2.1.I am trying to install 10.4.1What could be the issue?

Welcome to Apple Support Communities

You are installing an OS X version older than the one that came with your MacBook, so the hardware of your Mac isn't supported. See > http://www.everymac.com/systems/apple/macbook/specs/macbook-core-2-duo-1.83-13-s pecs.html

Call Apple to get replacement DVDs > http://support.apple.com/kb/HE57 They will include a Mac OS X version compatible, so you will be able to install Mac OS X

"you need to restart your computer"

Hi ... That's called a kernel panic.

Try these articles ...

Tutorial: Avoiding and eliminating Kernel panics

OS X: About kernel panics

In that case, you indicated a wrong OS X version. Check the links that Carolyn gave to you, because this may indicate a hardware problem

This Mac is really dated and it could definitely be a hardware issue. That's why it's generating kernel panics.

Approxiamtely 2006 ..

You would have to upgrade from v10.4 to v10.5 to v10.6 in order to install Lion. But that will not fix the kernel panic issues.

OS X Lion system requirements

To use Lion, make sure your computer has the following:

• An Intel Core 2 Duo, Core i3, Core i5, Core i7, or Xeon processor
• Mac OS X v10.6.6 or later to install via the Mac App Store (v10.6.8 recommended); you can install without Mac OS X v10.6 by using an OS X Lion USB Thumb Drive, available on the Apple Online Store
• 7 GB of available disk space
• 2 GB of RAM