I assume that when you say it does not catch, that means there is no indication of any attempt to fire. If so, the four most likely candidates (no particular order):
1) Fuel pump relay - located in relay tray behind the ash tray leftmost in the second row. See the FAQ for location diagram. (actually two relays in one package.)
2) Radio supression relay. Under the hood usualy on one of the shock towers or attached to a bracket on the coolant tank. It is black, aobut 2 1/2 by 2 by 1 inch. You should have two identical relays. The other one is for the electric cooling fan located in front of the radiator. Swap the two relays and see if the car starts.
3) RPM sesor mounted on the top of the bell housing between the engine and transmission. Be cautious if you go to replace this sensor because if you break it and if falls into the bellhousing, it will require dropping the transmission to retrieve the pieces. Much written about this in previous posts and in the faq -- read on.

4) Less likey, but needs to be on the list. The power stage for the ignition system is faulty. This item mounts to the inner driver side fender. It is about 2" by 4" by 12" thick with a 6 position connector going to it. Chck other things first and come back to this. 4.5) Coil is faulty - This can be checked with an ohm meter.

Short description of Starting Sequence: When you turn the key, relay number one in the fuel pump relay engages to enable several items including the radio supression relay which powers the fuel injectors. The ignition control system is also powered up at this stage. The ecu looks for pulses coming from the RPM sensor as the engine turns over. When these pulses are seen, the second relay is activated by the ecu to turn on the fuel pumps. If all is well, the engine now starts. As stated previusly, some models run the fuel pump for about two seconds to prime the system at startup.

Check your fuses, check to see if you hear the main fuel pump running and check for spark -- Simple and safe method: Use the neon bulb in a home electrical tester to sense for voltage in the spark plug wires. Just touch the bulb to the wire as someone cranks the engine. You should see a flash with each spark.

OK, if on the other hand the car tries to start but just will not run, it may be the air mass meter, amm. This is a black cylinder in the air intake hose after the air filter. If this is the case, with the key in the off position, disconnect the 6 pin wire connector from the amm and try to start the car. Note: make sure that you only remove or connect electrical connectors with the car off.) If it now runs, it is in "limp home mode". Post back and get some more help.

Good luck,
Dan

P.S. You are making some good steps by posting here. This is the best place to get advice for your 'new' Volvo. Now, find a good junk yard in your nighborhood and save yourself a bunch of $$$$$ for parts. The self serve or pick-n-pull places usually have the best prices.

What type of music do you play?