in c:\windows\temp, the answer is that is safe to delete them. There aren't many programs nowadays writing to c:\temp (that's more typical for old MS-DOS-programs, but if they do they know the rules and you can delete them also.
Don't you have a Recycle Bin as a safeguard against mistakes?
I did a search of my PC for *tmp files and it showed about 60 of these files in my Temp folder. Should they be there?