Use the computer you've been given for the tasks you need to do, but track the time it takes. Then do some back-of-the-napkin maths and figure out how much les

Use the computer you've been given for the tasks you need to do, but track the time it takes. Then do some back-of-the-napkin maths and figure out how much less time it would take with a more modern machine. Then calculate [yearly needless processing time in hours] x [the cost to employ you per hour] = [wasted company money]. Give this to your manager/employer and tell them this is the cost of you having a useless computer. Unless they are terrible at business and accounting this will get their attention.