If you have lost your original license key, you can retrieve it by checking your purchase confirmation email or contacting PST Walker Support with your registration details. OST to PST Licenses & Pricing - PST Walker Software
If you tell me what you're trying to do with your PST files, I can help you: deleted emails from a corrupted archive? Convert a large OST file to PST for a specific mail client? pst walker license key 118
For non-commercial use on up to 5 PCs with a 20 GB file limit. If you have lost your original license key,