In your original post you say that you had tried Ethernet and still had the slow speed problem. Did you have the Wireless Adapter disabled during the Ethernet connection test? If not, try the Ethernet test again with the Wireless Adapter disabled:- i.e.
Right-click the Wireless status icon located in the Task Bar,
select 'Open Network & Sharing Center',
Select 'Change adapter settings',
Right-click your Wireless Connection Icon,
Also, what is the make / model number of the replacement Wireless Network card?
As an alternative to internal Network hardware adapters you could consider purchasing a cheap external USB Wireless adapter, for example:-