Problems with Online Streaming Video, WMP Stalling, and General Internet Slowness

Hello,

I have a Dell XPS M1730 that came with Windows Vista Home Premium installed. For the first 8 or 9 months of use, everything seemed to work fine untill I started noticing that streaming video from online began to stall and require me to refresh a lot. At the same time, I noticed that when I attempted to play DVDs using WMP, the video would stop and I could not get it to start up again unless I closed down and restarted it over again. Repeatedly, it would give me problems like this but it would eventually play if I tried enough times. And of course, on top of all that, I noticed that using Firefox 3.5 or IE7, I was starting to get frequent "Sever Not Found" or "Page Not Found" errors, and I would have to refresh (sometimes several times) before I could connect to that page. Ever since I first started noticing this, the problem has gotten steadily worse and shows no sign of improvement. I have tried uninstalling Firefox and IE, then reinstalling them but the problem persisted. I have called the ISP (realizing that the ISP had nothing to do with WMP). The technician came out and tested my line using his own laptop and he said his worked fine. When he tested mine, he said packets were being dropped and that it was not the ISP but he suspected it was my OS or laptop. In Safe Mode With Networking, I have none of these problems. Everything works fine in this mode. I tried turning off all of my usualy startup programs and it still had not impact in solving the problem in Normal Mode. I used MalwareBytes to scan and I only came up with some Adware stuff which I deleted from my laptop, restarted, and nothing changed. Still problems. Does anyone know what I can do to resolve this issue? Thanks in advance for any useful suggestions.