Help repairing win98

[jordan123]

After my son tried to delete avg anti-virus off his compaq comp it has removed an important windows file. Does not start up in safe mode. Does load windows but most things have disappeared or don't work. Tried to restore win98 but says' setup does not work in dos'. I tried to change the order of boot currently 1 floppy 2 hd 3 cd but it will not let me change it.
Help.:

[Biggles77]

When you try changing the boot order, is it in the BIOS or do you have options during bootup?
Check that your floppy drive actually works. The O/S may try to boot but if the floppy disk drive (FDD) is broken, then it ain't going to boot.