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A modern ATA/100 hard disk is backwards compatible with older 'legacy' ATA interfaces such as ATA-2 but the data transfer rate will be limited by the ATA-2 interface spec which is 66 MB/second max, whereas on a modern interface the drive can manage 100 MB/second max in theory.
However, your main problem will be one of disk capacity. All new laptop disks today have a capacity of at least 20GB, even 40GB is the lowest capacity you can buy at many outlets. Your laptop may not be compatible with disks many times larger in capacity than the existing one. The new disk will work but you may find the laptop recognises only a fraction of it's true capacity owing to an old BIOS and other factors. See here:http://www.pcguide.c...d/bios/size.htm
As regards installing a Windows upgrade version, you don't need to install the older version first. Start installing the upgrade and setup will ask you to insert the older version CD so it can check it (you may have to 'browse' to the 'Win95' folder on the CD, I can't remember). When it's checked it, you put the upgrade CD back in and setup will continue.
Edited by pip22, 28 March 2008 - 09:26 AM.