Recently moved into a rental home. Older house, which has concrete external walls, and several internal as well where the house has been obviously extended. There are only two phone jacks, through an internal wall from each other. Study at the other end of the house.
Desk has a PCI wireless card. The signal registers as being very low, or none at all. Wife's laptop works fine through the house. Router is a Linksys WRT54G v5.

What can I do to improve or boost the signal?

Thanks in advance for any suggestions.