Normal pc @ 20k

Hi i am helping a perspn build his rig and he wants to use it for casual stuff and for learnin office and related courses as he has started working.Plz help me wit a rig which would last for 3 or more yrs.

1. What is the purpose of the computer? What all applications and games are you going to run? (Stupid answers like 'gaming' or 'office work' will not work. Be exact. Which games? Which applications? Avoid the word 'et cetera.')
Ans:Normal day to day use Surfing net,watching movies liistening music,playing some casual games

2. What is your overall budget? If you can extend a bit for a more balanced configuration, then mention this too.
Ans:20 k

3. Planning to overclock?
Ans:No

4. Which Operating System are you planning to use?
Ans:win 7

5. How much hard drive space is needed?
Ans:500 gb but i purchased one already

6. Do you want to buy a monitor? If yes, please mention which screen size and resolution do you want. If you already have a monitor and want to reuse it, again mention the size and resolution of monitor you have.
Ans: Yes

7. Which components you DON'T want to buy or which components you already have and plan on reusing?
Ans:Hard disk and mouse as i have bought

8. When are you planning to buy the system?
Ans: This week

9. Have you ever built a desktop before or will this be done by an assembler?
Ans:Assembler

10. Where do you live? Are you buying locally? Are you open to buying stuff from online shops if you don't get locally?
Ans: Hyderabad

11. Anything else which you would like to say?
Ans: Im building this rig for a friend who is takin there first pc which is for normal day to day use and would learn excel and other office related courses.