~ap5.tmp belongs to the Windows Media Player Codex for playing video files in the MPEG-4 format. It is a temporary file and not harmful in itself. However, it can become infected with a Trojan horse.
~ap5.tmp problems may be the result of malicious software, or may be unstable or corrupt for other reasons. We recommend a scan with ZookaWare PC Cleaner to remove unnecessary temporary files, and clean or restore any corrupt ones.