Reboots on W98 systems are often caused by running out of system resources.
After checking for viruses, there are a few more things to check.
Start by checking for an updated driver for your video card.
Next, do you have DirectX version 9 installed?
With many older video cards and drivers, DirectX 9 can cause a number of system problems.
If the driver for your video card does NOT support DirectX 9, you should remove DirectX 9, and install the latest version that is supported by the video driver.
You can find DirectX removal tools at www.voodoofiles.com
Next, run a check for Ad-Ware and Spy-ware using AdAware www.lavasoft.de and
SpyBot Search and Destroy.
(I use the link from www.nonags.com)
How much RAM and free hard drive space do you have?
For W98, you want between 128MB and 384MB of RAM, and at least 1GB of free hard drive space.
I recommend against using a fixed size page file for ANY version of Windows after 3.11.
You may be able to fix some problems by running a registry repair tool such as V-Com Fix-It, or Norton Win Doctor.
If a registry cleanup does not fix the problem, I do suggest a clean install of Windows.
You can get 90% of the benefit of a format and install by deleting the registry files.
Most of the benefit of a clean installation of Windows is that you start over with a clean and compact registry.
You will need to re-install all of your applications. But, your data files will be intact.
Chas