is there a way to open the trunk to my 1990 volvo 240 other than with a key? the key i have is different from the one to the trunk ...

There are 2 different keys for the door and the trunk? Are you sure? That is strange. There was no interior release for the earlier Volvos so I'm not sure how to get around it.

In the car has central locking (electric door locks), when you unlock the drivers door it should unlock the trunk. You will have to push in the (thumb) botton of course.

You should have 1 Key to open all the locks. There is master key and a service key. The Master key and the Service key are EXACTLY the same with one exception, the raised section running down the length of the grove of your key. if it is the same height all the way along to the rest of the key you have a service key. if it is slightly lower you have a master key. There is also the other possibility which is a pain in the butt is that the lock barrel is seized. Most owners simply use the power lock feature for opening and closing the trunk lock and never use the lock. The lock freezes up over from lack of use and then it is useless. You free it up but it requires lots of patience and time. The last one I did this too require complete disassembly and cleaning. Later,