25K is not enough
The config is already given by praveen.SO im just copy pasting it
AMD64 Athlon 3000+ (Socket 939) - Rs 6300
ASUS A8N-E - Rs 5600
Leadtek Geforce 6600 128MB Graphics card - Rs 6500
Seagate 80GB SATA - Rs 2800
i-Ball Cabinet with 400W Real power supply - Rs 1500
Transcend 2x512MB (1GB) DDR 400 - RAM - Rs 5000 (overclockable to 210 Mhz clock freq)
Total - 27.7 x 1000
If u r out of budget then get only 512 MB RAM.Its enough.

Get Altec Lansing ATP 3 speakers also if budget permits.They rock