Pain ain't they! From start go to Find then in the top space type *.tmp - click search and this will bring up all the files that are temporary. Click Edit | Select All and File | Delete. None of them are any good and take up space.
Temporary Internet files need to be taken out by Disc Clean-up. Click Start | Programs | Accessories | System Files | Disc cleanup and this will get rid of them.
Not a bad idea to get hold of Cleansweep, a great programme, that will keep you squeaky clean all year round.