- I have Pentium III processor. I want to replace the processor with the latest P 4 or something else.
- I have CD ROM drive. I am going fro DVD Writer. Is it dependent on the Processor ?
- My machines RAM is 256 MB. I want to replace with 2GB RAM...
OK, this I can respond to.
What you ask ... changing from a Pentium III to a Penitum 4 and increasing the memory to 2GB ... can not be done. More precisely, you would have to change your motherboard to do this. It is not physically possible to plug a P 4 CPU into the socket of a P 3 motherboard. The CPUs have a different number of pins. (Look at the socket column in these tables).
(BTW, that is not the only reason what you asked will not work. It's just a quickest way to point out one reason why it would not work).
For similar reasons you could not increase the memory of an old Pentium III motherboard to 2GB. The physical formats and underlying hardware support just would either not allow it or would cost you more than it rationally worth.
So if you want to "upgrade" then I think what you want is to get a newer computer, or at least replace your motherboard which a newer one. This would also require to get a CPU and RAM which would work in that motherboard.
As JohnB said in his answer, you'd do much better completely skipping the Pentium 4 series and moving to something "... made within the last 5 years ...". It's not just that you will get vastly better performance. It is also that, as he pointed out, you often actually can end up paying more for the older parts simply because they are now less available. The cost/benefit rarely makes sense.
Finally, a word about moving to a DVD writer. The price of a 5.25" DVD burner these days is around $20 to $40 depending on where you get it (at least in the US). DVD burners have become a commodity item. But again, you would do better running one on a more recent motherboard. The newer chipsets and CPUs provide better data throughput which in turn makes burning a DVD more reliable (IMO).
If the newer iCore series hardware (using DDR3 RAM) is not within your reach then I would suggest looking around for a Core 2 Duo motherboard & CPU which uses DDR2 RAM. (Or possibly a Core 2 Duo which uses DDR3 RAM ... I'm not sure which would result in the better deal for you).