My computer connects with a wireless router with a PCI card.  But every once and a while it will lose connection, and all my downloads and stuff are cancelled.  Is there anyway to prevent losing connection?

what is the signal strength between your PC and your router.

If it is quite low, then you need to move your router and PC closer together. Or, if your pc is under your desk, get an ariel extension cable.

My computer connection speed is usually low, but I was moving it around and lately it has been Very High  My computer is in my room upstairs, and my router is downstairs. 

It's likely because of interference of some sort it loses the signal. This wouldn't happen if they were close (and you can check signal strength in the control panel).

I had that problem a while ago.
What I did was go into the router settings and change the channel it was using to another channel. The problems never happened again since that.

I was using channel 11, but changed to 3.
May not work for you, but try changing channels, often solves glitches like this.

Thanks for the feedback  I will try these suggestions

you have a cordless phone?,, that sometimes can screw things up
also.. how far away are you from the router?..

and you can play with the antennas to see if that helps

I messed with the antenna and it has been working great since.  I just hope it keeps it up.

but why wont u move it closer to the computer? cant be done?

hmm yea mite wanna change channels or maybe move the router away from sometin that mite disturbe it..phone..maybe tv..radio.,i dunno much bout routers..

Cordless phones only interfere with Wireless networks when they use the 2.5(4 possibly? I'm not 100% sure)Ghz frequency. I have 5Ghz and 900MHz phones in my house and they work fine and do not interfere with my wireless connection.

Also make sure your conecting to the right network I know tith me there is a DEFAULT and a LINKSYS network i was coneted to default and my conection was very week and now it's conected to LINKSYS it's a strong conection and works great.