If you have two lists in Microsoft SharePoint 2010, [Hardwareitems] and [Hardwaregroups] and the list [Hardwareitems] contains a “foreign key” to the list [Hardwaregroups], you can customize the form of the [Hardwareitems] list to contain a drop-down list representing the [Hardwaregroup]. Than you can show the form on a SharePoint [InfoPath Form Web Part], by connecting the list web part to the [InfoPath Form Web Part], you can directly edit and create new items on the same page as the list. Make sure you set the Postback settings of the [Submit picturebutton] and the [New Item picturebutton] to “Always”. If you don’t set postback settings to “Always” the drop-down list box will not be reset on clicking the [New Item picturebutton]
Some screendumps:
Hardwareitems
Hardwaregroups
Add a “InfoPath Form Web Part”
Connect “InfoPath Form Web Part” and “List Web Part”
Action on “New item” picture button in InfoPath
Postback settings on “New item” picture button in InfoPath