Could you please post the error log details ?
If you want to run SQL Server 2005 or SQL Server 2008 on Windows 7, it requires installing the last Service Pack.
References:
How to obtain the latest service pack for SQL Server 2005
http://support.microsoft.com/kb/913089
How to obtain the latest service pack for SQL Server 2008
http://support.microsoft.com/kb/968382
Microsoft SQL Server 2005 Express Edition Service Pack 3
http://www.microsoft.com/downloads/details.aspx?familyid=3181842A-4090-4431-ACDD-9A1C832E65A6&displaylang=en
Microsoft SQL Server 2008 Express Edition Service Pack 1
http://www.microsoft.com/downloads/details.aspx?displaylang=en&FamilyID=01af61e6-2f63-4291-bcad-fd500f6027ff