well whats ur use?? i mean show off or do some work.. or u need to overclock the system ?? or need a home entertainment system ??
a general guide would be..
Processor : Core 2 Duo E6600
Mobo : Intel G965WH
RAM : 512*2 DDR 667
HDD : 120GB SATA 2
Graphics Card : umm.. may be 7300 LE as system needs to fit inside of 40k
Cabinet and SMPS : Any local with 450watts SMPS and good warrenty...
Monitor : LG / Samsung 17"
SKP : Xpree 2.1 (to me its enough) or rather u chose
Keyboard mouse : u choose...
P.S. get a pricing idea :
http://www.deltapage.com/