nope, not a valid test/way to reproduce the issue.

here's your exact code, but loaded with random data.

on my machine, with all four versions of SQL Server I have installed (2005/2008/2008R2/2012), it returned results in about 9 seconds.

CREATE TABLE [dbo].[temptable2](

[Field1] [varchar](23) NOT NULL,

[field2] [varchar](20) NULL,

[field3] [varchar](50) NULL,

[field4] [datetime] NULL,

[field5] [varchar](255) NULL

) ON [PRIMARY]

Create clustered index idx1 on temptable2(field1)

INSERT INTO temptable2

SELECT TOP 200000

LEFT(CONVERT(varchar(50),NEWID()),23), --23 chars

LEFT(CONVERT(varchar(50),NEWID()),20),--20 chars

LEFT(CONVERT(varchar(50),NEWID()),50),--50 chars

CAST(RAND(CHECKSUM(NEWID()))*3653.0+36524.0 AS DATETIME), --datetime

LEFT(CONVERT(varchar(255),NEWID()),255) --255 chars

FROM sys.columns T1 cross apply sys.columns T2

select field3,count(1)

from temptable2

group by field3