boot-up problems

Greetings,
My system will not boot(Windows XP Home/upgrade from ’98 SE), it gets to the initialization point and says that I have missing or corrupted files. The message I get is this…
The following file is missing or corrupted.
There are 3 files and they are… C:\Windows\Himem.sys, C:\Windows\DBLBUFF.sys, and
C:\Windows\IFSHLP.sys. Also another that comes up after that says that the WIN.COM files cannot be found.
Could you please direct me as to how I would reinstall these particular files and can I do it without having to reformat the HD.

Any help would surely be appreciated!

Thanks,
Steve