I have a Saab 900 and when I press down on the clutch pedal to change gear it makes a rasping noise? Could someone tell me please is this serious?
From your limited description, it could be one of two things:
First and most likely, your clutch could going out. When disengaging your clutch, if there is any metal-to-metal contact, it's going to may a louder noise than normal.
Secondly, it could be that the throw-out bearing is worn out. The reason I think this is less likely than the first is that the friction disk will usually wear out before the throw-out bearing will.
Either way, if one or the other is going bad, you'll want to get them both replaced at the same time. This is because both problems require you to split the transmission/engine. This means that the labor charge should be about the same for either or with both.
EDIT: I was just thinking, if you are saying the noise is actually a grinding noise (like when you are actually changing gears) it could be that your synchros are going out (or are pretty much shot) in your transmission. Your synchros allow the gears to match speed with each other and then go into gear easier without the grinding. It can make a lot of noise, but usually only happens in 1-2 gear or 3-4 gear (going either way), and then later on you might hear it in the other set of gears as well.
It's also possible that the noise is coming from the clutch pedal pivot, which needs lubrication. This problem surfaced a time or two during my ownership of a 1982 Saab 900T, and was remedied easily. Although I don't remember where I approached the pivot (from the passenger compartment or the engine compartment), I do remember that spray lube solved it, and all without serious disassembly. When my son sold the car it was 23 years old and had ~200K miles on the original clutch.