On a whim, I doubled and then some, my RAM on my HP Media Center Desktop (HP M260N) from 1 GB to 2 1/2 GB on my XP System (4GB is maximum RAM).
My Internet Speed, which was decent before on Roadrunner Cable, became superfast. So at least in my case, Memory did affect Internet Speed/Page Loading significantly. My Hard Drive is 120 gb of which about 115 GB is free.
I found an excellent place online to purchase Memory at
www.memorystore.com. This is an unsolicited endorsement of them. Their Web site is excellent matching the applicable Memory to your computer & they offer both their own Manufactured Memory & that of other Manufacturers. There was a huge difference in price between the 2. I bought 2 1GB RAM Modules of their Brand for only around $160 or so. The RAM obviously works great. Their Customer Service is Excellent as their technical department did a great job in answering my questions & explaining things to me. The good thing of upgrading is you can sell the RAM your replacing on Ebay so your overall upgrade costs are even lower.