Hmm, this text seems to be a bit outdated. There IS a way to turn DEP off in XP SP2, both system-wide and based on applications.
This is done as follows:
1. Click Start, and then click Control Panel.
2. In Classic View, double-click System.
3. Click the Advanced tab, click Performance, and then click Settings.
4. In the Performance Options dialog box, click the Data Execution Prevention tab.
5. Select Turn on DEP for all programs and services except for those I select, and then click Add.
6. In the Open dialog box, locate and select the application, and then click Open.
7. Click Apply, and then click OK. A prompt appears and informs you that you must restart your system for the setting to take effect. Click OK.
The avast update will be released during this month.
Cheers,
Vlk