How To Buy a Computer
I generally recommend that you purchase Dell computers although their reliability is generally no better than other manufacturers. You can see reliability ratings for computers here.
When you arrive at Dell's home page, you will have two choices: Home & Home Office or Small Business. Both websites sell very similar computers, however, the prices they charge are rarely identical. Most of the time, the Small Business division sells their computers for about $50 less than the Home division, but occasionally the reverse is true. My suggestion is to price your computer in one division, and then try the other division, to see which division is cheapest that week.
Your computer will probably come with one of several versions of the Windows 7 operating system. You can compare versions here.
Windows 7 comes in 32 bit and 64 bit versions. You can learn more about the differences between these two here.
Before buying a Windows 7 computer you may wish to determine whether all your existing hardware will work with this operating system. You can do this by downloading the Windows 7 upgrade advisor. You can also check compatibility of individual pieces of hardware or software.
You will want to get word processing software (and perhaps spreadsheet software) for your computer. If you want to buy Microsoft Office, the least expensive way to do that is to buy the MS Office Home and Student Edition, which is widely available at Office Depot, Microcenter, and Staples for $149, or even less when it is on sale, which is frequently. MS Office Home and Student edition is also available on some, but not all Dell computers. Home and Student edition contains Word, Excel, and Powerpoint. You can also get a product that is very comparable to MS Office called Open Office here. It is free of charge and has received excellent reviews.
You must have antivirus software on your computer, and I strongly recommend that you obtain antispyware software as well. I give you recommendations on the best packages for your computer here.
If you want to replace your Internet Explorer browser with a browser that is more secure, you have three good choices: Firefox (made by Mozilla) or Google Chrome or Opera.
If you need additional email software, you have several choices including Windows Live Mail or Thunderbird, both of which are free.
If you need software to work with and manage your digital photos you have two free choices: Microsoft's Photo Gallery or Google's Picasa.
If you are shopping for a printer, you can see reliability ratings here.