Using Dell Monitor Usb/ Card Ports Selling My Pc, Whats It Worth?

Selling my pc, whats it worth? - using dell monitor usb/ card ports

I want to make a new computer, what do I need a new PC, here is my current PC, please tell me what is its value:

Team:
Pentium 4 1.4 GHz or 1400MHz
640 MB SD-RAM
40GB Hard Drive 40 GB hard drive (slave)
Pioneer 16x Dual Layer DVD Burner
LG 16X DVD
Nvidia 64 MB video card, integrated audio, 2 USB ports, floppy drive, Ethernet card

Other hardware
Monitor Sony Trinitron 15 '
Dell keyboard, Logitech 3-button mouse

I bought the Millennium Development Goals in November 2001, so its almost 5 years, slowly, because I have so many things in it, but it works fine if you are surfing the net. This is a good piece, but times have changed and a new computer to the Internet through applications.

As for what I'm looking for, and between $ 400 - $ 650 Is this reasonable? The DVD that I bought a new DVD recorder has been purchased this year and is only 2 months, a DVD player purchased in 2002 and still functions as for the monitor, which I in 2003 and works very well!