MCSA/MCSE Self-Paced Training Kit (Exam 70-270): Installing ...

5-26 Chapter 5 Configuring Windows XP Professional
Important Only users with administrative rights can use the Performance Options dialog
box to increase the paging file size.
Paging files never decrease below the value found in the Initial Size text box that was
set during installation. Unused space in the paging file remains available to the internal
Windows XP Professional Virtual Memory Manager (VMM). As needed, a paging file
grows from its initial size to the maximum configured size, which is listed in the Maximum
Size text box. When a paging file reaches the maximum size, but a running program
still needs to allocate more virtual memory, Windows XP Professional will refuse
that allocation, which can cause an error, or even a crash, in applications.
When you restart a computer running Windows XP Professional, the system resizes all
paging files to the initial size.
Data Execution Prevention
Data Execution Prevention (DEP) is a set of hardware and software technologies that
perform additional checks on memory to help prevent malicious code from running on
a computer. In Windows XP Professional, DEP can be enforced by compatible hardware
and by software.
Note DEP is an update included with Windows XP Service Pack 2. Hardware DEP is available
with compatible devices and runs only on the 32-bit version of Windows XP Professional
and Home Edition.
Hardware DEP works by marking all pages in memory as non-executable unless the
page explicitly contains executable code. This process helps prevent malicious
attacks that try to insert and run executable code into memory. To use hardware DEP,
a computer must have a compatible processor that allows Windows to mark memory
pages as non-executable. Both Intel and AMD provide hardware DEP–compatible
processors.
Software DEP is a set of security checks that can run on any processor capable of running
Windows XP. However, the security provided by software DEP is limited compared
to that provided by hardware DEP.
You can configure DEP by using the Data Execution Prevention tab of the Performance
Options dialog box. By default, DEP is enabled for only essential Windows programs
and services. However, you can turn DEP on for all programs and services, and then
select specific programs and services for which you do not want DEP enabled.