Hi there!
I think my old computer has some BTC in it but it's an REALLY old computer (since 2009 I think),
what's the most useful - risk free way to check if I do have any bitcoins in it?
It wont start, I mean it does but crashes
In summary,
1. Look for the file "wallet.dat". Make a copy and keep it safe and do not share with anyone (in case it is not encrypted).
2. Install bitcoin core on a new computer. Replace the new wallet.dat with the recovered wallet.dat. Let it synch (or re-scan if already synched).