How to determine the appropriate page file size for 64-bit versions of Windows Server 2008 and or Windows 2008 R2

http://support.microsoft.com/?id=889654

Method 2: Use the Page File Bytes Peak
counter to calculate page file size

1.    
Click Start,
point to Administrative Tools, and then click Performance.

2.    
Click System
Monitor.

3.    
In the
right pane, click + (the Add button).

4.    
Click Use
local computer counters.

5.    
In the Performance
object list, click Process.

6.    
Click Select
counters from list, click Page File Bytes Peak, click Add,
and then click Close.

7.    
Let the
counter run during typical use of your computer.

8.    
Note
the maximum value for the Page File Bytes Peak counter, and then
multiply the value by 0.70. The sum of the equation is the size to set for your
page file.