Loud fan means the heat sink is getting clogged with dust/debris and is no longer properly transfering heat. It can also mean that the thermal paste has dried out.

Either way, vacuum the vents first. If it's still loud, it's probably the beginning of the end. Copy your save files and anything else that you want. If you're brave, you can take it apart and reapply new thermal paste. Use a quality brand.

I'll definitely try vaccuming, but I can't back up, as the HDD is 320gb, and I have no external hdd which is that big

You don't need an external HDD that is that big. How much space has save files taken on your system? That's all you need.

Everything you have downloaded from the PSN, you shouldn't worry about it. You can download it again. Game data can be installed again.

Just make sure to format your external HDD or a flash drive to fat 32.

Mine i bout at Canada on Gamestop or something like that with extended warranty (3 years), but the common one is just 1 year my friend... sorry to know your PS3 is going to let you down... just buy 3 more.

The fat PS3 will do that if it's in a space that isn't properly ventilated. I used to have a 60GB console and it would be loud when the room was too hot because the fan had to work harder to cool the system down. It's actually normal and the console will warn you if it's about to overheat. Still though, I'd recommend you move it to a cooler area or just run an oscillating fan pointed directly to it.

The thing is, I have taken a look at the back, and it look completely clean, no dust or anything at all. I have made sure to keep my PS3 in a well ventilated area and there is definitely nothing blocking the fans, so I am keeping my fingers crossed

As for backing up, I know I don't need all the room, but if I want to use the back up utility, then I do need the room. Copying all my save files is rather annoying and time consuming

if it makes you feel better, i have a 40gig fat model. The fan has been goin on overdrive since February. ITs still working fine right now and I played and finished FFXIII, Resonance of Fate, and Dragon Age Origins on it and I totaled about 400 hours of game play on just these three games.

change thermal paste and correct way to put thermal paste is on youtube.