There are two types of Upgrade approach from SharePoint 2007 to SharePoint 2010.
Consider this scenario,
In these situation you cannot use the In-Place upgrade approach.
So you need to upgrade your server or farm to support the 64 bit application then migrate your 32 bit SP 2007 to 64 bit application.
Then you can start the actual In-Place upgrade. It requires lot of efforts and time consuming and costly process in term of upgrading the hardware and software.
Simple approach for the above scenario is "Content Database attach" method. Before this your SQL Server meet the following requirement. It must be updated to SQL Server 2005 SP3 and the n Upgrade to SharePoint 2010 and move your content database to this new set up and connect this server to your SharePoint 2010 Farm.