SSD install, where??? on ASUS S101

As long as the OS is installed on the hdd you have installed, yes.

short answer because it needs it.
long answer
because the HDD needs 1 to 2 amperes of current to start the motor and you PC will not do that.
they do sell Y cables for USB. for 2 usb in to PC
and 1 usb end to HDD external case.
for more power.
but the external ac/dc 2amp pack is best.
it is best for using the external,drive on any PC
for the reasons stated (proof) below.
see this chart?, see why the top 4 will not work
if hdd draws 1amp startup (WD5000LPCX)as seen here

https://datasheet.octopart.com/WD5000LPCX-Western-Digital-datasheet-104459145.pdf


1.0amps startup current if above is your drive. spec.
there you go , a short and long answer, can go longer, easy. ask.



http://www.pcdied.com/external-hdd.html

Yes, if your computer supports 32GB SSD, it will support 64GB and 128GB and 256GB.

you cannot change or upgrade your HD to SSD. SSD is a technology in which storage medium is not a disk but a Memory chip just like USb flash drive.
However you can exchange your driver with SSD

As an alternative, you can try making a new Time Machine backup from the files of the old HDD. Install Mavericks from scratch on the SSD and then transfer the documents needed back from the Time Machine.

I would recommend installing fresh OS X when upgrading from HDD to SSD anyway.

Here is how to make a bootable USB stick for installing Mavericks:
http://www.youtube.com/watch?v=2or1Wthkl1w

Do you need any additional assistance?

update your drivers and check the cables out as well

control panel admistrive tools,computer management,device manager scroll down universal serial bus controllers you should see a yellow question mark?
right click to reinstall drivers or
ports(com&lpt)right click update driver or
scroll to disk drives if you can see your drive + to expand right click you should see options to update driver,disable,uninstall scan for hardware changes. or
select properties you should see options in the general tab to troubleshoot,policies,volumes,driver and details under the driver tab you will have the options to check the driver details,update driver,rollback driver or uninstall
hope this helps

Try this link at the bottom of it there is another link to You Tube about the Ram, fingers crossed it helps you out.
If it does please give Thumbs up thank you..

http://www.ultimate-netbook.co.uk/Asus/Asus-Eee-PC-S101/Asus-Eee-PC-S101-Memory-Upgrades/Asus-Eee-PC-S101-2-GB-667-Memory-RAM-Upgrade___279.htm

Hmm, did the drive come with a few pins to be used? The pins, when attached correctly would make the SSD either slave or master... it could be that currently its set as slave, hence the BIOS would make some problems... have you tried that?