If you need to access your Linux EXT3 partitions on Vista OS system with full write and read access first you should download the Ext2Fsd Project software on your computer.
By using Ext2Fsd software, you can access Linux partitions and modify the content of these partitions.
You can download the program from the following link;
After installing the program you will see a GUI such as the following one;
From that screen; you should first start the Services for accessing these Linux partitions.
Go to the partition you want to access and right click on it and click Service Management from the menu.
On this menu, you should click Start button for starting the partition access and click Apply button.
(You may need to right click and choose Change Driver Letter option from the menu to assign a drive letter for the Linux partition.)
After that operation, you can access these partitions from the Windows Explorer (You should use the driver letters assigned.) and you will have both read and write access on these Linux partitions.
There are other alternatives for accessing Linux OS partitions from Windows OS such as the following programs.
DiskInternals Linux reader http://www.diskinternals.com/linux-reader/