2GHz can get much slower than that these days and there generally isn't much to be gained from going all out on MHZ for what you are doing. Unless you are crunching photos all day every day.
I tend to stick to the Seagate HDs and get the 7200RPM drives with 8MB cache and the 3 year warruntee. The 3 year warrunttee version are only a few dollars more and well worth it. The faster spinning drive will have a noticeable positive effect on load times and general sense of performance more than most other things. You aren't going to get much more performance out of a SATA interface than a ATA100/ATA133 since the current drives aren't able to saturate the ATA133 interface let alone start using the higher bandwidth of the SATA interface, but the cost difference is negligible so either is fine. At the moment the 200GB drives seem to be the best value for money so start looking at region and work up if you feel the need for more space, but since this is a desktop you can always add another HDD further down the track as the need arises.
512MB would be the minimum but 1GB would be nice if you do a lot of image processing. but again this can be upgraded down the track too.
Firewire, USB2, Ethernet, etc its all pretty standard these days but you might find that serial and parallel ports have vanished on some motherboards so be aware of that if you need them.
You can get motherboards which have a decent 3D card built into them and they also have and additional AGP slot to expand as required but you end up sacrificing PCI slots for this. Unless you are going to be playing DOOM3 and the like then a middle or the road 3d video card (something with a ATI RADEON 9250 or X600) will be more than enough. AGP is fast being replaced by PCI Express as the preferred graphics interface so make sure that the card you choose has the same interface as your motherboard.
They cost nothing and are handy in emergencies so I'd throw that in there.
Double layer DVD+/-RW drives have come down a lot in price so I'd recommend getting one of these.
depends on your cash and desk space.....LCD or CRT your choice, just make sure the picture is clear, some of the cheaper LCD monitors don't have as clear of a picture as you may require.
Buy your Operating system and Office package with the hardware so you can get OEM licenses (Windows requires any old piece of hardware but Office requires a MB, HDD and CPU to be on the same invoice). Unless you are involved in the academic industry then you can get Academic licenses of office and make it a bit cheaper again.
Places like http://www.tomshardware.com/
do regular comparisons of monitor s and motherboards etc so have a quick look through there and pick out the best of the bunch, after all oils ain't oils and motherboards ain't motherboards.