Right, I have automatic updates set. And I looked under "my computer" but don't see where it shows Service Pack 1 RC1 Build.

This is the detailed error message when I get the error "Windows Explorer has stopped working", then if I open details it has this:
Problem signature:
Problem Event Name: APPCRASH
Application Name: Explorer.EXE
Application Version: 6.0.6000.16549
Application Timestamp: 46d230c5
Fault Module Name: ntdll.dll
Fault Module Version: 6.0.6000.16386
Fault Module Timestamp: 4549bdc9
Exception Code: c0000005
Exception Offset: 0002294f
OS Version: 6.0.6000.2.0.0.768.3
Locale ID: 1033
Additional Information 1: bfef
Additional Information 2: e8adce1c2b9e7be834b4063ac3c53863
Additional Information 3: bfef
Additional Information 4: e8adce1c2b9e7be834b4063ac3c53863

I looked under UPDATE HISTORY and it shows that Microsoft SQL Server 2005 Express Edition Service pack 2 (KB 921896) was successfully installed. But I see nothing about a Service pack 1