I just bit the bullet on my five year old computer. I decided to give the innards a clean - never been done before.
I looked up a lot of info on the internet and decided to go with the leaf blower clean.
Took the computer out onto the verandah, took off the sides, made sure I had all the visible fans stabilised so that they couldn't spin and stood back a bit a let loose with the leaf blower.
You should have seen the dust and junk that came out!
Gave the case a bit of a wipe over, put it all together and brought it back inside.
Waited for a little while, then started it up.
It started up beautifully and is now so quiet that I have to lean in to make sure that the fans are actually working.
It was struggling at very high temperatures, it's now running about 10C cooler.
Not a remedy that everyone would recommend, but I thought it was worth a try for me, and it seems to have worked quite well.