Acer Aspire One's SSD(Solid State Drive) has been criticized for its slow read and write speed. Intel lists the drive's maximum speeds as 38 MBs read and 10 MBs write. While the SSD in the Acer Aspire One has average read times, it suffers from very slow write times. Acer Aspire One's that come shipped with XP have 120GB HDDs that dont suffer from these slow writing times. While there are many ways(Like using Win XP instead of Win Vista or Win 7) to speed up Acer Aspire one but its better to just replace the SSD with an HDD if write times become a problem.
1.8'' PATA HDD will plug directly into the connector used for the SSD. It requires almost no fabrication to fit, and the BIOS automatically detects the drive.
eBay is filled with used 20GB HDD and larger drives in this format, so this modification can be relatively cheap to perform.
Here is a link which includes video with step-by-step instructions:
Video