I used Virtual PC to create a virtual machine with configuration:
CPU: Intel Pentium E6300 2.8Ghz overclocked to 3.66Ghz (which supports VT technology)
RAM: 600MB
I thought it was enough for me to install SQL Server 2005 enterprise on it. But installer still tells me that the virtual machine does not meet the hardware requirements. Did I forgot something about this?
Are you trying to install the 32 or 64 bit version. Microsoft Virtual PC only supports a 32 bit virtual OS. For reference here are the system requirements for SQL 2005. http://www.microsoft.com/Sqlserver/2005/en/us/system-requirements.aspx
You didn't. It is not a supported configuration, hence the warning.
It should run OK, but I would avoid this for anything other than development/test (in which case developer edition would be simpler).
Check the MS web site for what virtualisation solutions are supported with SQL Server (and other server software).