There are far too many advantages with an assembled computer.U can get the best in the market in ur computer though it is not off much use(eg.Samsung hd which comes with 3 years warranty which we are not likely to get with branded ones)
The main problem I find with branded ones is the cost of software(esp OS) and the extra tax we have to pay as a whole, which I feel is quite unnecessary.
The assembled computer will have a great advantage if its processor is AMD.Its saves u more then 4, 000Rs, but some vendors point out that it gives a lot of heat and is big mess.after all they want more business.AMD is as good as Intel.AMD is definitely faster in speed performance on an overall it is same.So if u have an AMD chip, then u can afford for 17inch flat screen monitor.optical mouse and an woofer system for ur comp.instead of a 40gb hd 60gb( I mean(cost of 60gb hd-cost of 40bg hd).all in that 4000rs saved in chip cost.so a better look and more pleasing isnt it.
If we consider only Intel chips then on an overall in terms of cost we easily save more then 5, 000 just for the same branded pc because of those extra taxes and for the costly Windows OS.In very few cases it is free of cost, but with assembled ones.we always get for free(of course a pirated one.but still the job is done).
In assembled ones it is that u can have the best inside ur comp if u can afford, but with branded ones we rarely get such a combination.like p4 2.4, 60gb hd, cd-rw, 256MB ram, 17 inch flat screen monitor, wireless keyboard, and mouse(optical), woofer(if AMD), 440W speakers.we may get branded ones with this configuration but it likely to cost more then 50K but assembled its not more then 38K.If its AMD it is still cheaper.
Rarely do people get problem with synchornization of all of there components when its an assembled one.It has never happened for any of my friends or for me.Get informed about the components nicely and see hows the components ar being assembled.This is very important.because we no longer have to use our computer like a black box, which is likely in the case of branded ones.
Lastly, id like to point out that in branded ones there is always expert help readily available.which is not available with assembled ones.but in most of the cases it is not necessary, because if its a hardware problem.u can always get changed form the vendor.just a little pain(which is not likely in most cases)for who r willing to take the best.