There will almost certainly be problems, but with drivers, not necessarily
shortcut keys. You can probably find the drivers, but this could be quite
time consuming and very frustrating.
It's also a very bad idea as XP is a much better system. Perhaps if you
explain what is prompting this thought we could be of more assistance. Many
people are overwhelmed by XP, but it can be set up to act  and look very
much like 98/ME.
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Can you format a laptop hard drive that has windows XP on it and then
replace it with Windows ME without any problems?  On the case it says
designed for Windows XP.  I thought that, if nothing else, the short cut
keys might not work?

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