Apart from the 'one time' download (with no updates or email support), LW offers Pro ($ 21.95 for free updates & email support for 6 months) or Extended Pro ($34.95 for free updates & email support for 12 months).

Providing that you bought one of these options from the official site Official Website & Free Download - Lime Wire (payment to LimeWireLLC will show on your reciept & CC statement) then your download period won't have expired yet
Your Pro personal download page has details of when your benefits expire - on the right hand side at the top of the page you'll see 'Your Order Details'... this will show you when your benefits expire.

I don't use Windows 7 but...

Does your account have administrator privileges? If not, change the account to include admin privileges.

Also, you could try changing the location for saving files within your browser's settings... maybe saving downloads to a different location will make a difference?

If you can take a screenshot of the error or tell us exactly what it says, maybe another Windows 7 user will have some answers