Is there any way to clean the power supply?

It depends on the version of your xbox. Blowing air through the vents helps very little due to the type of fan and the way the air channels are designed. The fan cannot be reached directly with a duster nozzle.

The surest way to clean the fan is to open the power supply. (This should be done with the power supply unplugged for 30 minutes or more for the capacitors to have had time to self-discharge.)

The supply can be opened by removing the rubber feet on the bottom of the supply. However, the first and second Xbox 360 revisions (Xenon & Zephyr) have glue filling up the screw holes moking it very difficult to remove the screws. The best way to overcome this is to heat up a screwdriver with a lighter or other heat source and quickly and firmly plunge it into the hole. Continue this until the driver can reach the screw.

The newer versions (Falcon & Jasper) have rubber feet attached to plastic plugs that are relatively easy to remove.

Once open, the fan is accessible under tiny screws so make sure that you have a jeweler's phillips screwdriver available.

To prevent this from happening again, keep the power supply at least one foot (0.3m) from the floor.