SQL 2005 Express Edition Installation Failure

I'm trying to install SQL 2005 Express Edition in a PC running Windows XP Proffesional Edition SP2. I have .Net Framework 2.0 properly installed. I downloaded the software but setup is not working. This is the log registering the problem:

Microsoft SQL Server 2005 Setup beginning at Wed Sep 12 07:51:27 2007
Process ID : 2796
f:dc17aef5dcc0f0613f2745378bsetup.exe Version: 2005.90.1399.0
Running: LoadResourcesAction at: 2007/8/12 7:51:26
Complete: LoadResourcesAction at: 2007/8/12 7:51:26, returned true
Running: ParseBootstrapOptionsAction at: 2007/8/12 7:51:26
Loaded DLL:f:dc17aef5dcc0f0613f2745378bxmlrw.dll Version:2.0.3604.0
Complete: ParseBootstrapOptionsAction at: 2007/8/12 7:51:27, returned false
Error: Action "ParseBootstrapOptionsAction" failed during execution. Error information reported during run:
Could not parse command line due to datastore exception.
Source File Name: utillibpersisthelpers.cpp
Compiler Timestamp: Fri Jul 29 01:13:55 2005
Function Name: writeEncryptedString
Source Line Number: 124
----------------------------------------------------------
writeEncryptedString() failed
Source File Name: utillibpersisthelpers.cpp
Compiler Timestamp: Fri Jul 29 01:13:55 2005
Function Name: writeEncryptedString
Source Line Number: 123
----------------------------------------------------------
Error Code: 0x80070002 (2)
Windows Error Text: El sistema no puede hallar el archivo especificado.
Source File Name: cryptohelpercryptsameusersamemachine.cpp
Compiler Timestamp: Mon Jun 13 14:30:00 2005
Function Name: sqls::CryptSameUserSameMachine:rotectData
Source Line Number: 50
2
Could not skip Component update due to datastore exception.
Source File Name: datastorecachedpropertycollection.cpp
Compiler Timestamp: Fri Jul 29 01:13:49 2005
Function Name: CachedPropertyCollection::findProperty
Source Line Number: 130
----------------------------------------------------------
Failed to find property "InstallMediaPath" {"SetupBootstrapOptionsScope", "", "2796"} in cache
Source File Name: datastorepropertycollection.cpp
Compiler Timestamp: Fri Jul 29 01:13:50 2005
Function Name: SetupBootstrapOptionsScope.InstallMediaPath
Source Line Number: 44
----------------------------------------------------------
No collector registered for scope: "SetupBootstrapOptionsScope"
Running: ValidateWinNTAction at: 2007/8/12 7:51:27
Complete: ValidateWinNTAction at: 2007/8/12 7:51:27, returned true
Running: ValidateMinOSAction at: 2007/8/12 7:51:27
Complete: ValidateMinOSAction at: 2007/8/12 7:51:27, returned true
Running: PerformSCCAction at: 2007/8/12 7:51:27
Complete: PerformSCCAction at: 2007/8/12 7:51:27, returned true
Running: ActivateLoggingAction at: 2007/8/12 7:51:27
Error: Action "ActivateLoggingAction" threw an exception during execution. Error information reported during run:
Datastore exception while trying to write logging properties.
Source File Name: datastorecachedpropertycollection.cpp
Compiler Timestamp: Fri Jul 29 01:13:49 2005
Function Name: CachedPropertyCollection::findProperty
Source Line Number: 130
----------------------------------------------------------
Failed to find property "primaryLogFiles" {"SetupStateScope", "", ""} in cache
Source File Name: datastorepropertycollection.cpp
Compiler Timestamp: Fri Jul 29 01:13:50 2005
Function Name: SetupStateScope.primaryLogFiles
Source Line Number: 44
----------------------------------------------------------
No collector registered for scope: "SetupStateScope"
00E3CFC4Unable to proceed with setup, there was a command line parsing error. : 2
Error Code: 0x80070002 (2)
Windows Error Text: El sistema no puede hallar el archivo especificado.
Source File Name: datastorepropertycollection.cpp
Compiler Timestamp: Fri Jul 29 01:13:50 2005
Function Name: SetupBootstrapOptionsScope.InstallMediaPath
Source Line Number: 44
Class not registered.
Failed to create CAB file due to datastore exception
Source File Name: datastorecachedpropertycollection.cpp
Compiler Timestamp: Fri Jul 29 01:13:49 2005
Function Name: CachedPropertyCollection::findProperty
Source Line Number: 130
----------------------------------------------------------
Failed to find property "HostSetup" {"SetupBootstrapOptionsScope", "", "2796"} in cache
Source File Name: datastorepropertycollection.cpp
Compiler Timestamp: Fri Jul 29 01:13:50 2005
Function Name: SetupBootstrapOptionsScope.HostSetup
Source Line Number: 44
----------------------------------------------------------
No collector registered for scope: "SetupBootstrapOptionsScope"
Message pump returning: 2

I don't understand why this is happening and any help is appreciated (I don't wan't to install MySQL!!!!). Thanks.