Yes you can access your files on the old HDD.
Set the jumper on your old HDD to slave.
There should be a diagram on the HDD showing which setting the jumper needs to be on.
It doesn't matter whether the HDD is SATA or IDE.
Setting it as a slave will allow you access to its contents.
When you PC reboots after installation, run the BIOS setup and add the HDD - some BIOS may do this automatically.
It doesn't matter that the OS are different.