This is more of a "trying to get some information" than "oh my god, what to do" post.
Yesterday, I finally had it with my computer overheating all the time and I realized I haven't changed the thermal paste for over than 2 years. It was full of dust as well, so I thought I'd give it a good clean.
So I did; I vacuumed the largest dust particles, wiped off the smallest ones, cleaned the old thermal paste from my CPU and GPU with 91% alcohol and a cloth intended for cleaning glasses (doesn't fluff, doesn't carry static electricity), re-applied thermal paste and put it back together.
The computer works fine, but the problem is that it seems that the GPU fan is louder than before. This might be my imagination, but I don't see much improvement in the temperatures as well.
The CPU cores are running well, as its temperatures stay between 33 ºC and 40 ºC when browsing the web or running code editors (3 - 4 ºC improvement).
The GPU temperatures haven't changed that much (45 - 58 ºC, currently running at 57'C). I guess I should have compared the temperatures when running a game or anything that stresses the GPU, but currently I'm just a little concerned about whether I've been changing the thermal paste correctly all this time and haven't I damaged my hardware.
As shown in the picture, I applied about a pea sized amount of paste in the middle of the processor, then reinstalled the cooler without smearing the paste as this is what I was taught.
My questions are:
Should I be worried about the temperatures?
My video card is a GeForce 9400GT with 1 GB of memory used for nearly 4 years.
How often should thermal paste be replaced?