Bumpff.
Have a look for a folder called options on your system (use explorer tools and find) In the folder you will probably see loads of files called ".cab"s and with a bit of luck a setup.exe. This is usualy a copy of the win98 and the drivers for your system along with all the other preloaded software.
If you can copy the folder off to a cd if you suspect a dodgy disc or if you're feeling really brave run setup from the options folder and re install windows on top. Doing the back up is throughly recommended though.
This is certainly true for quite a few machines such as Dell and Packard bell, that come in pre installed, I suspect that evesham either use the same technique may be with different names. once you have found loads of .cab s you have found the windows setup.
Good luck
Rickity