I was using the official Bitcoin client some time ago. It was version 0.5 I think. Then my computer crashed and didn't use Bitcoin for a long time.
I was lucky because I had a backup of the wallet. Today, I installed the latest version and it's different. It is running for many hours now but it's still at 18-20 %.
Should I leave it as it is or I can turn off my PC and continue tomorrow?
If I use my old wallet, will it start from the begining? If yes, is it better to stop the software, delete everything, replace wallet and start all over again?