Deleted Log Files

How can we recover deleted log files? I made a boot system scan and Avast! found 2 viruses. I went to a vacation but when I returned my antivirus had expired. I needed details of the viruses so I could prevent them in future. Can anyone tell me a way of recovering deleted log files. Pls-(There was no log file in the program and Application Data).

What deleted log files ?

What was detected, file name and location ?