Guys after hearing this i decided to return it to my friend but how should i begin making my own pc as i don't have the money yet to buy all the parts now so i thought let me first get the really basic things first like a chassis and motherboard
If you don't have money, you do the "Low Budget" move. It's a manouver with several points - you progress along the line if you still can't afford it.
1. You *need* to buy a CPU, a Motherboard and compatible RAM memory, that's Computers 101. The CPU should have a boxed radiator for it - all you have to do is make sure that the socket is compatible and mount the CPU in the Motherboard according to the instructions provided with the set. General Rule? "If you're posh, you get Intel. If you're cheap, you get AMD". Of course this is an over-exaggeration, but AMD usually has "cheaper" alternatives to Intel, even if they're less efficient. Dual-Core CPU's are the current standard, if you can afford a Quad-Core, get one. As far as Memory is concerned, 2GB is today's "safe minimum" - you shouldn't get any lower then that. 4 is recommended, anything over that is more then welcome. Make sure to divide your memory into two (or any other even number that your Motherboard supports - usually they have 2-4 slots) modules to create a Dual Channel set unless you are positively sure that you will buy a second module soon. Do your best to buy two identical modules for the set (for compatibility's and performance's sake) however sticks of different brands should be perfectly compatible. Corsair and Patriot > Everything else. GoodRAM's are "good" if you want some cheap RAM memory fast - I can recommend them.
2. You *need* a PSU - if you're building a gaming rig then you need to add the Wattage of the CPU (usually anywhere between 100W and 150W), the GPU (If present, 300W or more - refer to the box the card came in) and misc. (leave about 100W of a margin), making a circa 600W PSU the optimal, reasonable and minimal choice. This is one of those parts that you don't have to invest "much" in if you don't have to - a steady PSU is obviously better however a salvaged one may serve you just fine for the time-being. Make sure your PSU is SATA-ready.
3. You need a hard drive. You can salvage one from an older computer to make-due, you can also buy a new one. The capacity is for open debate, really - just buy one that'll give you enough storage. If you can afford it, buy the fastest one you can get. Don't look at SSD drives - they're too expensive for a small budget. Optical drives are what you want. The general rule is Western Digital > Samsung, I suppose > Seagate > Maxtor > All the other crap that's out there. If you want to feel safe with your data, don't go cheapo on the drive. Make sure it's a SATA drive - ATA drives are a dying breed, only use them if you have a salvaged one. Worst case scenario = install your OS on a USB stick if you can't afford a drive at the moment.
4. You need a graphics card. You go either of 2 ways - buy an NVidia card or an AMD (ATi) card. This is really a matter of taste, so I suggest simply looking up some benchmarks and checking the ratio of Quality/Price that you feel comfortable in. If you *CANNOT* afford a Graphics card at this time, make sure that the Motherboard you purchased has an on-board Graphics chip. You're going to make-due until you get some cash to invest more.
HINT: Supposedly AMD cards work better in conjunction with AMD CPU's, although I'm not quite sure whether that's true or not.
5. You need a chassis, but it's not a "vital" part. In fact, you can have a computer up and running even without one, so unless you have the bucks for it, don't invest much in it. You can always change the chassis and it's usually not that expensive to swap.
6. You can buy misc. crap of all-sorts - bigger radiators, fans, heat spreaders etc. etc.
Go from the top of the list, eliminate stuff you cannot afford as you go down the list. This is really "Computers for Dummies" so it'd be great if you got some advice from the shop clerk, however don't let him/her sway you too much - if they sniff the "newbie" from you, they WILL try to sell you stuff you don't really need/want.