Old socket 478 processors can not be used in 915 chipset motherboards.this one supports LGA775 type processors.As for as ur memory and HDD,u can use the present ones on the new board.
for more info visit:-
http://www.intel.com/design/chipsets/915g/
Gigabyte GA-8I915G-MF supports Intel P4 LGA 775 Processor+ Intel 915G Express,costs Rs.11000
MSI 915P Neo2 Platinum Edition supports Intel P4 775 Processor+ Intel 915P Express costs 12500
Asus P5GD2 Premium Intel P4 775 Pro+ Intel 915P Express Rs.19450
MSI 915G Combo-FR Intel P4 775 + Intel 915G Express Rs.8500
INTEL D915GAV Intel 775 + Intel915G Rs.7000
Asus P5GD1-VM-UAYOZ Intel P4 775 + Intel 915G Rs.7900