Cant update from OS X 10.7.5 to Snow Lion

You may upgrade Lion only to Mountain Lion if it meets the other requirements:

Apple - OS X Mountain Lion - Read the technical specifications.

Macs that can be upgraded to OS X Mountain Lion

1. iMac (Mid 2007 or newer)

2. MacBook (Late 2008 Aluminum, or Early 2009 or newer)

3. MacBook Pro (Mid/Late 2007 or newer)

4. MacBook Air (Late 2008 or newer)

5. Mac mini (Early 2009 or newer)

6. Mac Pro (Early 2008 or newer)

7. Xserve (Early 2009)

Please do not post serial numbers.

If your model is a mid/late 2007 or later, then yes. Open System Profiler in the Utilities folder. From the information displayed on the right look for:

Model Identifier: MacBookPro3,1

You must be that or late (such as MBP 4,1) to run Mountain Lion

Im not able to update my OS , as it says ur computer not compatable , im currently on OS X Lion

Then your system is not compatible with Mountain Lion.

The data you provided about your Mac is conflicting. You claim to have a MacBook Pro, but to my knowledge only MacBooks shipped with GMA X3100 graphics sections.

Click on the Apple Menu's "About This Mac," "More Info," to properly identify your Mac.

The MacBook4,1 (13", Early 2008, Late 2008 Polycarbonate) is not capable of running Mountain Lion. Lion is the limit. The MacBook5,1 is the minimum requirement for Mountain Lion.

You need to correct the info in your TAG.