Old laptop - Refurbished or Replaced?

I do have a question for you.Let say that you have spent quite a lot of money in purchasing a notebook five or six years ago and now it is quite obsolete now. Despite the age, the notebook still always but one or two bits are not working properly due to wear and tear. My question would be whether you would rather replace the parts or just throw the laptop away and buy a laptop instead?

As for me, I would just try to replace the parts that are spoilt. Well, I went a step further. I did some research into the best part that the laptop could take it (e.g. if the laptop only had a CD-RW on it, I would fix a DVD-ROM combo into it. If the hard drive is spoilt, I will get the largest hard drive that the mobo can handle. I think for older laptops with IDE, the largest 2.5" Internal HDD that I can find is 160GB. I would really appreciate if other people can tell me any larger HDD for the IDE interface.

I got rid of the 1.4Ghz and replaced it with a 2.2Ghz which it is superb! Now, the laptop is even better than when it was new!!! The speed boost was evident as I have increased the memory from 768MB to 2GB! It is a pity that I could not change the graphics card as it is not a MXM. It is also not Nvidia graphics to start off with. Now, I find that the laptop is pretty good! It is so much faster than before.

The bad part is that I am stuck with a single core pentium 4 mobile cpu. I have no choice because the BIOS will not recognise any better mobile chip than this one. Even if the BIOS can handle the dual core cpu, the fan and heatsink might not make it so just leave it at 2.2 Ghz pentium 4 mobile.