i write sale prices as "regular price"-"discount"="sale price"
CPU: $75- athlon x3 440 (office people just dont use 4 cores)
http://www.newegg.com/Product/Product.aspx?Item=N82E16819103843
Mobo: $65- Gigabyte 760g, micro atx
http://www.newegg.com/Product/Product.aspx?Item=N82E16813128408
RAM: $94- Kingston hyperX 4GB, ddr2 1066, cas 5
http://www.newegg.com/Product/Product.aspx?Item=N82E16820104073
Case: $40- CM Elite RC-103 (who says an office pc cant have a side view window?)
http://www.newegg.com/Product/Product.aspx?Item=N82E16811119203
PSU: $44-$4=$40 SeaSonic 350 watt, 80 plus bronze
http://www.newegg.com/Product/Product.aspx?Item=N82E16817371033
HDD: 110-10+50 intel 40 gig SSD + WD blue 320 gig (oh ya.. thats right)
intel- http://www.newegg.com/Product/Product.aspx?Item=N82E16820167025
WD- http://www.newegg.com/Product/Product.aspx?Item=N82E16822136074
DVD: $20 lite on, 24x, good reviews
http://www.newegg.com/Product/Product.aspx?Item=N82E16827106333
graphics... on board
that comes to 499 with regular prices
or 485 using the sale prices
so if sale prices are allowed then the extra money would go to a bigger hard drive or an athlon x4 or shipping if that is not included in the 500
i think that by sacrificing a little in each area, a SSD would make the system much more snappy and 40 gig is plenty for an OS and office applications.. and actually could be used for everything except videos and music and maybe pictures.
I chose triple core because office pcs rarely do more than 2 cpu intensive tasks at a time
it is am2+ but you really dont gain much by going am3 and ddr3 except for maybe upgrade ability
the psu is 80+ bronze so it will be quiet and cool, 350 watt is plenty of power and you could easily add a low level gpu if you wanted
the case is quiet and good looking with ample airflow, but most 40 dollar cases would be fine
thats my build

Its not designed for regular office people though... lets be honest those people would be fine with dual core 2 gig systems... but its what you can do for 500