1.4? Are you running XP? An i5 W/4G is sure up to running curren 2.X calibre

Configure the Avire (or other brand) to Exclude the Library folder for
active scans (the books have been scanned before you ADD)

Defrag your HD , THEN defrag the Pagefile (get that Sysinternals tool from MS).


ckeck your Windows Virtual memory settings. It should not be OFF or overly small (meet or exceed suggested or Let Windows Manage)
If it was not for the second start works, I might have suspected a corruption in the Calibre config

Do you have any NETWORKED DRIVES or Cloud backup configured?