By default, you cannot do this with the Advanced search or by sorting by column because Quantity on hand and Quantity Forecasted are calculated fields.
A workaround is to export your whole list to csv and filter in Excel. (note: you can save export lists if you need to do this often)

I found this module:

https://www.odoo.com/apps/7.0/stock_filter_none_zero_qty/

It is also available for 6.1 - I didn't test it yet, but it looks promising.