and sorry for your loss.
You might do a file search for “wallet.dat” on his computer(s), and search the entire disc(s), including subdirectories, and hidden files.
Note which directory it is in. If it is in a “bitcoin” directory, you may have found the wallet. If you did, then just try and launch his bitcoin client (program) and see if you can access the wallet data. If it somes up, it will show you a balance.
If there is no balance, then any BTC that he had, might have been kept in an “exchange” wallet, or paper wallet, somwehere on the internet.
if there is a balance, it can be transffered to another wallet, or sent to an exchange for cash value. It could, possibly be protected by an encrypted password, which you would have to figure out, before you can do anything with it.
Look for a text files, also, (.txt file), that may contain his login and password(s). These could be under any one of a number of programs, like microsoft office, notepad, wordpad. etc.
You need to give a bit more information, sowe can help more.
Which operating system was he using (windows 7, windows xp, etc)
This might let us tell you a bit better, what to have you look for.
Otherwise we are all guessing.
I keep mine information in a text file, called “(something)_login.txt”, and I keep them encrypted, but I always keep a copy of the password. He ,might, also, keep them on a usb stick, if you see any laying around, which is the safest way to keep them.
You ,might look for any file on the disc, named “bitcoin*.*”, with your file manager, under “search”…or files named “exchange.*”, or any file with an exchange’s name, such as “mtgox*.*”. This might give you a starting point.
I can give more explicit instructions, if I know what operating system he is using (windows 7, windows xp, etc)
If you were close to me, I could come do it for you, for free.
Others might charge you a fee.
If the file in encrypted, it may be a bit harder to access, as you would have to try and figure out what passwords he might use.
One thing I might, also, suggest, is that of you have a computer geek friend, let him/her have a look around on the computer, to help, but keep an eye on him/her, as I trust no one. Don’t let anyone remove anything, period. Make them work on it then and there.
BTC is worth a lot of money,, and you could loose a substantial amount, if he has been doing this for a while.