It depends on if you want to upgrade your old machine or buy a new one.
Obviously upgrading is more cost effective than buying a new one and it’s going to be kind of a bear without the proper equipment, but there’s a few ways to do it that aren’t so bad.  We always encourage people to reuse their current equipment to reduce unnecessary ewaste whenever possible. But depending on how much he uses it, and what you’re doing daily, sometimes it’s just time for a new computer.
That said I can give you the run down on the two DIY methods.

A) Reusing the old computer.

Before getting started its always good practice to back up the data of the computer beforehand. He would need the disc for windows 7, and also would need to make sure his machine meets the minimum requirements for the software to be used effectively and would also need to know if his computer was a 32-bit or 64-bit system. Then it’s a simple matter of popping in the disc, booting up the computer from the CD, and letting the program run. Once the computer gets to the install window, he’ll have to choose custom install, and then select the partition of where he wants to install the new OS. Usually the biggest partition. Do Not Format the partition. The software should carry all of the existing information in the user profile over to a folder on the hard drive called “windows.old” that can be carried over once the installation is complete. Then once windows is activated and updated. He should be able to navigate to the C drive and copy all of the information from his old user profile into his new user profile (the one created when the new windows was installed). It would be a copy from “C:windows.oldUsersName of old profile” transferred to “C:UsersName of new profile”. Pretty straight forward so long as the guy doesn’t use accounting software like quicken or quickbooks, or mail software like outlook. Also if he uses mozilla favorites, those have to be transferred a different way as well.

B) Buying a New Computer.

Unless you have it custom built from Dell or someone, most new computers come with windows 8 or 8.1.  Not a huge deal just something to keep in mind if he’s not the sort that adapts well to change. The process is a bit different. Without an external slave or a network hub, the most elegant way to transfer the data from his old computer to his new computer depending on the amount of data (c:usersname of profile *right click* properties), the data can be transferred with dropbox. Just upload all of the user data to dropbox, let it complete, and then pull it down on the new computer with the same account info and drag it over into the new user profile. For larger amounts of data a usb drive or jump flash drive could be used. It would be the same operation, navigate to “C:Usersprofile” pull all of the data, and navigate to the same location on the new machine and transfer the data over, then make sure to merge all folders.

For multiple accounts on the same computer it gets real hairy real quick. But for singles users, it’s pretty straight forward. The whole operation takes about 3 hours.