Internet Slowdown And Random Disconnect

Recently I bought a new PC to replace an old laptop that I use in my bedroom. However, initially I couldn't pick up my downstairs router signal. So, I bought a new wireless network card and STILL didn't pick up any signal. I then purchased a Netgear WN200RPT and everything seemed to be ok while using that to repeat the signal up into my bedroom. Then, suddenly, it all stopped working. The WN200RPT would, although showing a full internet connection with no yellow ! or red x's, it would never ever load webpages. So, I removed it and put it back in its box. Then, for some unknown reason after a Windows 7 reinstall, my network card started picking up the signal from my home router and had a good speed and signal. This worked fine for a month or two before it started playing up again. It would randomly slow down and stop loading webpages, or completely lose the signal and show a red x, stating that no signals could be found. The strange thing is, all the other PCs in my house connect wirelessly fine, and so did the laptop that was in the same room as this PC. After a system restore, the internet started working again. Then it stopped. Another restore later, it works. Now it's intermittent again.