The best way to avoid fragmenting the pagefile is to isolate it on its own partition. Create a partition big enough to hold the pagefile, with some room to spare.

To move the pagefile to a new partition, right-click My Computer and select Properties. When the System Properties dialog box opens, click the Performance tab. Now, click Change and then set the maximum and minimum pagefile sizes to zero. Click Set to record your changes. Next, select the new partition and re-create the pagefile in the new partition (enter the original size in megabytes and click Set). Click OK to close the Virtual Memory dialog box, then click Close to dismiss the dialog box. Since you made a change to the system, you will need to restart the computer.

With the pagefile isolated from the data and application files, it has little chance of getting fragmented, and defragmentation programs will work more effectively on the rest of the drive."