I would suggest you to go for at least 250 GB.
As per your budget you can go for Seagate Barracuda 7200.12 Series ST3250318AS 250 GB 7200 RPM 8 MB SATA 3Gb/s Internal Hard Drive one of the most popular in the market.
It will cost you Apprx. Rs. 1,712.
Even if you go for 100 GB the difference...