Help me diagnose intermittent Windows hangs

I am getting regular system 'freeze' on a relatively new Win7 build. System is all different components put together a few months ago. Windows 7 install went without issues, except for this lingering problem.

Symptom is that the PC hangs. The PC is not totally un-responsive, but it could not start new processes or finish existing ones. The mouse is responsive to motion, but I can't execute anything new. If I hit CTRL-ALT-DEL I can bring up the spinning Windows icon, but the actual Task Manager window will not appear until the 'hang' cycle is complete. The system will hang in this way for about 30 seconds at a time. Eventually the system will clear this issue and become normal again.

Edited to note:

The PC just got hung again when I posted this thread. These events were in the log at the same time as today's hang:

Event ID 7036
The Windows Error Reporting Service service entered the running state.

Event ID 4672
Special privileges assigned to new logon.

Subject:
Security ID: SYSTEM
Account Name: SYSTEM
Account Domain: NT AUTHORITY
Logon ID: 0x3e7

Privileges: SeAssignPrimaryTokenPrivilege
SeTcbPrivilege
SeSecurityPrivilege
SeTakeOwnershipPrivilege
SeLoadDriverPrivilege
SeBackupPrivilege
SeRestorePrivilege
SeDebugPrivilege
SeAuditPrivilege
SeSystemEnvironmentPrivilege
SeImpersonatePrivilege

Event ID 4624
An account was successfully logged on.

Subject:
Security ID: SYSTEM
Account Name: PADO-PC$
Account Domain: WORKGROUP
Logon ID: 0x3e7

Logon Type: 5

New Logon:
Security ID: SYSTEM
Account Name: SYSTEM
Account Domain: NT AUTHORITY
Logon ID: 0x3e7
Logon GUID: {00000000-0000-0000-0000-000000000000}

Process Information:
Process ID: 0x2c0
Process Name: C:\Windows\System32\services.exe

Network Information:
Workstation Name:
Source Network Address: -
Source Port: -

Detailed Authentication Information:
Logon Process: Advapi
Authentication Package: Negotiate
Transited Services: -
Package Name (NTLM only): -
Key Length: 0

This event is generated when a logon session is created. It is generated on the computer that was accessed.

The subject fields indicate the account on the local system which requested the logon. This is most commonly a service such as the Server service, or a local process such as Winlogon.exe or Services.exe.

The logon type field indicates the kind of logon that occurred. The most common types are 2 (interactive) and 3 (network).

The New Logon fields indicate the account for whom the new logon was created, i.e. the account that was logged on.

The network fields indicate where a remote logon request originated. Workstation name is not always available and may be left blank in some cases.

The authentication information fields provide detailed information about this specific logon request.
- Logon GUID is a unique identifier that can be used to correlate this event with a KDC event.
- Transited services indicate which intermediate services have participated in this logon request.
- Package name indicates which sub-protocol was used among the NTLM protocols.
- Key length indicates the length of the generated session key. This will be 0 if no session key was requested.


I do have these errors in the event log, but they don't seem to correlate to the times when my PC gets locked up:

Errors in the system logs:

Event ID 7000:
The AODDriver4.2.0 service failed to start due to the following error:
The system cannot find the file specified.

Event ID 36888
The following fatal alert was generated: 70. The internal error state is 105.

These errors don't happen at the same time, and Error 36888 is more common.