Vanishing program query?

I have found that a program of mine has vanished off the pc but no one has actually uninstalled it, could malware be to blame?

ps the following prefetch file appeared in a search today

a~nsisu_.exe

also disk cleanup ran due to low space but I cant believe it would remove an entire program, any help is greatly appreicated

If it was uninstalled without my knowledge is there a way of finding out when it was uninstalled or anything like that???

Is there any info about it into avast logs?
Can you discover the path of that file?

I suggest a boot-time scanning:
Start avast! > Right click the skin > Schedule a boot-time scanning.
Select for scanning archives.
Boot.