Well... sites like www.ibuypower.com
will let you buy a PC for a very decent price an theyll build it for you. But personally, I recommend doing it yourself if for no other reason than all of the learning that will take place in the process!
If you arent too familiar with PCs Id recommend against SATA hard drives. Mine gave me a bit of a headache and Ive been doing this stuff for five years now.
DVD-ROM drives also act as CD-ROM, so you only need a DVD drive, then a CD-RW if thats another thing you want this PC to do.
Ill work on a shopping list for you when I get a sec, but as for now heres a shopping list to go by:
Case (ATX form)
CPU Heatsink (one will come with a retail processor, but I recommend you buy a nicer one)
Thermal Paste (a conductivity compound that goes between your processor and heatsink)
Modem/Network card (if needed, most nice motherboards have built in network cards)
Operating system ?
Any questions you have about those products, please ask- for now I need to sleep but Ill be happy to answer any questions later on.