If you just want some advice on computers and really don’t want to learn how they work, here is a short list of buying tips:
How Many cores?
When the chip makers ran out of ideas about how to make a CPU run faster, they added additional cores to make it do more work in the same amount of time. Generally everybody can benefit from a second core, because it lets you do something in the background while continuing to work on the machine. A third core gives you a little bit more power very infrequently. A fourth core is used only when compressing TV programs to download to your iPhone. Servers can use as many cores as they can get, but two cores is the sweet spot for a desktop or laptop.
How Much Memory?
A laptop typically has a maximum of two modules of 2G each. A desktop can typically hold four 2G modules. However, to use more than about 3G of memory, you have to be running the 64 bit version of Vista or Windows 7. This is why most new machines come with the 64 bit version of Windows 7 Home. Most people can probably run fine on 2G, but if you insist on leaving every program on your machine open and running, 4G is a safer bet.
A laptop only has room for one disk, and to extend the battery life this disk probably runs at lower power with less performance. This is the one point where using a desktop instead of a laptop makes a big, big difference.
Solid State Disks (SSD) that use flash memory chips instead of a rotating magnetic surface, can deliver 200 megabytes per second read and 100 megabytes per second write. Since they have no moving parts, jumping around from file to file is quick. This will provide the fastest system startup time and good performance for frequently used programs. However, this type of storage is expensive and cannot be sensibly used for large media files. If you have an SSD, use it just to hold the system and small programs. Put big files on a second regular disk, and if you have a laptop make that disk an external disk connected by USB or eSATA.
If you copy large files around a lot, say by recording TV programs to disk and then editing out commercials, then having two regular hard drives will provide the best performance. Put the unedited files on one disk and the edited files on another. Multiple disks also simplify keeping backups in case a disk fails.
Serial ATA (SATA) disks can simply slide into a docking adapter. For $30 you can buy a square box that sits on your desk and connects to a laptop or desktop computer with either USB or the faster eSATA (External SATA) cable. Drop a bare hard drive into the box and (with eSATA) this exteral disk will run as fast as any internal disk and will be faster than the disk in a laptop. Then if you want to change what you are doing, you can remove one disk and put in another disk with different data.
Therefore, when looking at laptops, try to find one with an eSATA plug, or in new laptops a USB 3.0 connector which is just as fast. The main disadvantage in laptop hardware (the slow disk) can be overcome if you keep an external 3.5 inch hard drive on your desk at home and on your desk at work and use them when you need better disk performance.
Screens, Keyboards, Mice
No laptop will compare to a big desktop screen, full sized keyboard, and comfortable mouse. Fortunately, you can have all three on your desktop and simply plug them into the laptop. Use the small screen and keyboard on the laptop when you are on a train or plane. If you mostly use your computer in specific locations that you can set up with full sized devices (and external hard drives) then you can buy a smaller laptop that is convenient to carry.