Technical sir i want to change my PC and want to buy a good one .one with a good graphics card 2GB ram 250GB HDD and other good faturs what will be its cost please help me soon

I'm a new expert to this site ... so I apologize if I'm stepping on the previous expert's toes, but as I've recently built a new PC fitting your description I have a very good feel for the current going rates.

I'll give you a description & ballpark estimate for a low-priced modern high performance PC with good overclocking capabilities & upgrage potential. It's what I would call a starter system with which you can explore the home computer market's latest and greatest hardware features. As you gain experience with this system and learn which of its features and components are the most important for your computer use it's extremely likely that you'll add things like; more ram, additional video cards and other pci cards, fans and other coooling solutions, hard drives, etc...
to optimize the system to your exact liking. The following is a very good starting point however.

You'll need all of the following:

1) Motherboard that supports a modern multi-core processor, multiple graphics cards, up to 8GB of ddr2 RAM. It should have built in hi-def audio, multiple USB ports (I prefer at least 8), multiple SATA ports (I like at least 4), at least one IDE connector, at least 2 PCIe 16x 2.0 slots, and a built in gigabit netword controller. I'm not including all the features that these boards usually come with ... once you've constrained yourself to the above requirements the type of board you want will become clear.

2) CPU & CPU fansink ... I reccomend a dual core processor that clocks at 2.5GHz or faster. It will most likely come with a stock fansink which work just fine in my experience.

3) 2 GB of DDR2 RAM ... I suggest 800 MHz ram from a reputable high performance name brand

4) A modern graphics card that supports a multiple graphics card configuration (ie, you can buy a 2nd card later, connect it to the 1st one and get an impressive increase in performance). It should have at least 512 MB DDR3 RAM & a GPU that clocks at 600 MHz or greater.

5) A case. There's a huge variety of products available in this category. It really depends on your personal tastes. I reccomend starting with a mid-ATX tower with a price tag under $100.

6) A power supply unit (PSU). I suggest getting getting a supply that has at least 2 PCI express connectors, 4-6 SATA connectors and can put out at least 500 W ... more if you can afford it ... mine is 750 W and I wish it was 850 W.

7) 250 GB hard drive ... get a SATA II drive with at least 16 MB of cache and spins at 7200 RPM.

8) Optical drive ... I suggest a SATA dvd/cd reader/writer ... that is, it can read and write both CDs & DVDs. Also, there's a technology called lightscribe where you flip the disc over and the burner actually burns labels onto the disc that look very professional. It doesn't cost more than an extra 5 or 10 dollars.

9) Keyboard & mouse ... whatever you're comfortable with. I like a large keyboard with a soft keys that light up. A standard optical or laser mouse with 3 or moure buttons and 1 or more scroll wheels.

All of the above will run you approximately $1000. You'll have to shop around on-line to get the price down to $1k ... but it can be done. At the end of the day you'll have a very powerful & expandable PC that's capable of running any of your favorite programs.

Hope this helps ... let me know if I can clarify anything. I've done my best not to promote any particular brands or products as I believe it's considered poor form to do so on this site.