Monitor your Task Manager. Right click an empty area of the Taskbar (bottom) and click Task Manager. Watch the Processes tab. When you freeze your CPU usage will probably be 100%.
If so look on the list of Processes and see if you can determine which process is using the CPU.
Also:
Look in your Event viewer: rt. click My Computer then click Manage then Event Viewer.
Or: Administrative Tools/Event Viewer or Start/Run/ eventvwr
Open the system as well as the application tabs & look for red
X errors. Click error line for details.
Post back the source & event id & Description especially of errors that seem to coincide with this issue.
Also check the Information lines that might coincide with this issue.
How to view and manage event logs in Event Viewer in Windows XP
