I'll combine your posts into a single one, again.
Post 1: With the reduced capacity of SSD's, file size becomes very important. It is easy to fill up a hard drive 128GB in size with multimedia. For instance, on my PC, Windows occupies 10GB, my programs (I'll admit I have a huge drive so I don't remove applications that often, yours would be half to a quarter of mine) take up 110GB, my music, a combination of WMA Lossless and MP3, take up 23GB, pictures take up another 5GB, and video another 150GB. Before long, you could run out of space, then you would need to upgrade a drive. Keep in mind that my PC has a TV tuner in it, along with a high-end sound card, so I have a large amount of video and my audio is as close to CD quality as you can get.
Post 2: Laptops are not highly upgradable, unlike a desktop. On a laptop, you can add more RAM, install a new hard drive, and maybe a new optical drive. You cannot upgrade the CPU, the screen, nor the graphics card. Using that link you provided, your old PC was good a few years back. Frist, the CPU technology is old and inefficient, second, the RAM only goes to 2GB, third, and finally, the graphics are simply awful. My old Vaio I got when I went off to university (2003) had similar specs and a better graphics card. I had to replace the laptop three years later since it was so painfully slow. If you have a good antivirus, like NOD32, your computer should not be slowing down due to adware and all the other nasty things the Internet throws at it. The PC simply may not be able to handle the newer stuff that is out. 12 to 13 inch laptops aren't that powerful and editing and watching multimedia on them can be painful. Laptops of that size are typically considered secondary computers, powerful enough to get on the net and do a few things, but lacking in the power department. Many laptop users get, or build, a good desktop PC, then spend little on a laptop since the desktop computer has all the processing muscle.
Post 3: You cannot upgrade a laptop. You can usually replace the RAM and the hard drive, but everything else is off limits. This is why, if you're planning on having a laptop be your one-and-only PC, to get the best you can afford. Many laptop makers have Windows 7 upgrade programs,
here's the one for HP,
here's the one for Dell,
here's the one for Toshiba,
here's the one for Sony. Manufacturer's love to hide information on the program, for some reason. Chances are, you won't be keeping the laptop until it breaks, it will get too slow one day and you'll need to buy a new one. In the $1000 plus category, there are more powerful options available. The
ASUS G Series G51VX-X2A,
SONY VAIO FW Series VGN-FW495J/B, and the
ASUS N81 Series N81Vp-D1 are all good alternatives. The more powerful the PC, the less battery life you get. Tack on a good screen and battery life dips to 2 or 3 hours with everything on high.