Hi Mike098,
Your dad has enough resources to try my suggestions which have three essential elements:
(1) Try Mozilla Firefox Portable browser version 2.0.0.20 (not any other version)
(2) Try Mozilla Thunderbird Portable email version 2.0.0.21 (not any other version)
Then if your dad likes Firefox and Thunderbird;
(3) Try Xubuntu version 8.04 or version 8.10 (not 9.04)
Re:
(1) google search "firefox portable 2.0.0.20" and download, then install it on your hard drive - make the install to location C:\.... then make a desktop icon
(2) google seach "thunderbird portable 2.0.0.21" and proceed as for Firefox.
After installation and testing he can delete both installation files.
I suggest these two programs because he would not actually need to use much else in Xubuntu other than, merely as a precaution, the Xubuntu (debian) on demand version of Avast (which there currently are no published plans to discontinue).
Also,
* They are not so different from IE and Internet Express and I suspect your dad will be fine with them.
* IE favourites are easily imported into Firefox, and all Express email data is easily imported into Thunderbird.
* Both these are easily transferred to Xubuntu and can be run as Windows programs from within Xubuntu.
* Xubuntu can use the latest versions of both Firefox and Thunderbird if your dad wanted to use them directly instead of via "wine" for windows.
If your dad likes these two programs then there are some excellent and useful add-ons, especially for Firefox, which I or others can tell you about, but first things first.
Also, if you google search "ubuntu absolute beginner" click on the top help sticky, then click on the first post you can download a 170 free book on Ubuntu (Xubuntu is a derivative), and also see lots of other information.
Now, if you have broadband you could run Xubuntu from a CD (burned from the downloaded ISO) or
since you have lots of time you could order a free CD (even free of postage)
or for immediate delivery you could buy a CD for around 10 dollars, pounds or euros.
However, BEFORE any Hard Drive installation it would be BEST to have a Windows clone just in case.
Below is a picture of my Xubuntu screen. On the left is a fairly standard Xubuntu menu shewing detailed Accessories with the red arrow pointing to Debian Avast.
On the right are 12 W98SE programs I can load with the aid of "wine" and "portableapps".
Xubuntu can be versatile and complicated but if your dad's main aim is security it can be very simple any many of its programs are easily and intuitively usable.
Your dad will be able to load W98SE as normal, only changing to Xubuntu when he wants to.
Xubuntu is intrinsically much safer than Windows and it is often a lot faster than W98SE.
My regards