You see new shiny machines with Core 2 Duo CPUs and more for 399 so try half that. The monitor you say is worth that. Sorry it's used and no warranty.
Try ebay to see what its going for.
the ultimate HP digital entertainment experience, the HP Media Center m280n comes standard with the wireless HP Media Center Premium keyboard and mouse, enabling users to interact with their Media Center home entertainment PC from most anywhere in the room in which it resides. The new keyboard is also thinner and lighter than before with quieter keys than previous keyboards.??The m280n features a 3.0-gigahertz Intel Pentium 4 processor with Hyper-Threading Technology and an 800-megahertz front-side bus; 512-megabytes DDR memory; an enormous 200-gigabyte (7, 200 rpm) hard drive with plenty of storage space for recorded television and other digital content; both DVD+RW/CD-RW combo and DVD-ROM drives; and a 128-megabyte NVIDIA GeForceFX 5600 AGP 8x graphics card.
includes 19" LCD monitor sony