By default, Windows XP is configured by Microsoft to automatically restart during a fatal error or a stop.

Windows XP assumes when Ad-Aware is gathering drive info, that Ad-Aware has stopped (or had an error), so Windows restarts.

Altering the following settings should correct this.

Right-click 'My Computer',
Click the 'Advanced' tab,
Click 'Settings' under 'Startup and Recovery', '
UNCHECK the 'Automatically restart' check box under 'System Failure'.

If you uncheck this check box, you may receive an error message if a stop or error occurs.

Please let us know if, and what error you receive.

Microsoft Knowledge Base Article - Q320299