I need to amplify wireless signal/set second access point

There are a few options available to solve your problem.

Depending upon the type of router you have, you can get some custom firmware which enables you to increase the broadcasting power of your router. Of course, this only helps for routers which don't already broadcast at full power. The Linksys WRT54G is one of those routers.
Of course, you will want to manually connect to the router to update the firmware, just to avoid any lost data, which might permanently destroy your router. This would be the course to take if you don't mind getting onto one of your brother's computers for a little while to set up, the destruction risk, and you don't want to spend any money on another router

The safer option is to go out and purchase a wireless network range extender, which you can place at some halfway point between the router and yourself, and it should just rebroadcast the signal. I'm not entirely sure how these are set up though, as I've never had to use one, but its definitely something you can look into.

Jam it back in, in the dark.

Awesome. Glad I could be of help. =)

I've also noticed that often times, when I have a connection to a router right on the outskirts of an adequate transmission zone, that that area will gradually decay over the course of a few days to a few weeks, depending upon the load of activity.

Good luck.

How ya doing, buddy?