How much could I get for this old system?

I was given a Dell XPS 400 (made in 2006). I don't need it as I have a vastly better rig, so I want to sell it, but I have no clue what to ask for it. Any ideas?

Here are the specs:
Dell XPS DXPO51
- Full tower case
- Motherboard : Dell 0YC523
- Chipset : Intel i945P
- Processor : Intel Pentium ViiV dual core @ 2.8GHZ
- Memory : 1GB (2 x 512 DDR2 @533MHZ)
- Video Card : ATI Radeon X300 SE w/128MB memory
- Hard Disk : Maxtor (160 GB)
- DVD-Rom Drive
- Network Card : Intel PRO/1000 PL Network Connection
- Operating System : Windows XP