The major retailer is Flipkart. Another option is Primeabgb, and theitdepot is another one.
For now I will make a list using flipkart, but cabinets are not available on Flipkart, specially not good ones.
This is assuming that you are not buying a keyboard, monitor and such.
Motherboard
ASRock 970 Extreme 4 Motherboard Rs. 6464
Graphics Card
Sapphire Radeon HD 7850 2GB GDDR5 Graphics Card Rs. 14610
Internal Hard Drive
WD Caviar Green 1 TB Desktop Internal Hard Drive (WD10EZRX) Rs. 3881
Processor
AMD FX 8350 Rs. 11832
Ram
G.Skill RipjawsX DDR3 4 GB (2 x 2 GB) PC RAM (F3-12800CL9D-4GBXL) Rs. 2100
Psu
Corsair VS550 550 Watt PSU Rs. 3440
Amount Payable:
Rs. 42327
Add a case of your choice, preferebly the Cooler Master HAF 912 Combat version, or any other mid tower.
I went for an AMD build because of your budget, and even then managed to shoot it by around Rs.6000.
If you want a compromise, you can reduce the HDD to 500 GB and I can choose a lower end graphics card, preferably the HD 7770.
I chose this one because gaming and video editing is more graphics intensive rather than processor intensive. Thus a good GPU and a relatively low end processor can still grant an awesome gaming experience.
If you want an Intel build the price shoots up even more, because Intel overclock capable processors is the i5 3570K and the Motherboard costs more than the AMD one.
Which city/state do you live in?