Xbox Hard drive...

[*Long*]

so Yesterday I finally got the RRoD so i thought No problem!!! I'll return it to best buy and they'll give me a new Xbox. I thought I would be able to keep the old 20GB hard drive but they told me oh no! the 20GB is not compatible with the newer pro (Which comes with a 60GB hard drive only 40GB more) so they told me a data transfer cost $59.99 (USD) so i asked why cant they just slap on the old hard drive on the newer Xbox and they said its an older model! this pissed me off really good so i want to ask you guys... If i have the older 20GB and slap it on to the newer version of the Xbox pro will it work???