Can I install Windows XP to an SD card?

Have a 15 GB SSD drive on a netbook and running out of free space.  Can XP/XP Pro be run from the SD card in this machine?.. Then install applications to the SSD?

Unlikely.

How much of the 15GB is your stuff versus installed applications?  Could you put YOUR stuff on the external?

In the end though, 15GB - pretty anemic.  You may have to invest in a larger drive or a secondary drive where you installyour applications and put your data.

Do some house cleaning and dust off that hard drive:

You may wish to free up some disk space (will also aid in getting rid of things you do not utilize) by going through these steps:

Windows XP should take between 4.5 and 20GB *with* an Office suite, Photo Editing software, alternative Internet browser(s), various Internet plugins and a host of other things installed.  In most cases, particularly with XP and the applications most people use there, the numbers are closer to being under 9GB.  Everything else is the user's stuff.

If you are comfortable with the stability of your system, you can delete the uninstall files for the patches that Windows XP has installed...
http://www3.telus.net/dandemar/spack.htm
( Particularly of interest here - #4 )
( Alternative: http://www.dougknox.com/xp/utils/xp_hotfix_backup.htm )

You can run Disk Cleanup - built into Windows XP - to erase all but your latest restore point and cleanup even more "loose files"..

How to use Disk Cleanup
http://support.microsoft.com/kb/310312

You can turn off hibernation if it is on and you don't use it..

When you hibernate your computer, Windows saves the contents of the system's memory to the hiberfil.sys file. As a result, the size of the hiberfil.sys file will always equal the amount of physical memory in your system. If you don't use the hibernate feature and want to recapture the space that Windows uses for the hiberfil.sys file, perform the following steps:

- Start the Control Panel Power Options applet (go to Start, Settings, Control Panel, and click Power Options).
- Select the Hibernate tab, clear the "Enable hibernation" check box, then click OK; although you might think otherwise, selecting Never under the "System hibernates" option on the Power Schemes tab doesn't delete the hiberfil.sys file.
- Windows will remove the "System hibernates" option from the Power Schemes tab and delete the hiberfil.sys file.

You can control how much space your System Restore can use...

1. Click Start, right-click My Computer, and then click Properties.
2. Click the System Restore tab.
3. Highlight one of your drives (or C: if you only have one) and click on the "Settings" button.
4. Change the percentage of disk space you wish to allow.. I suggest moving the slider until you have just about 1GB (1024MB or close to that...)
5. Click OK.. Then Click OK again.

You can control how much space your Temporary Internet Files can utilize...

Empty your Temporary Internet Files and shrink the size it stores to a size between 64MB and 128MB..

- Open ONE copy of Internet Explorer.
- Select TOOLS - Internet Options.
- Under the General tab in the "Temporary Internet Files" section, do the following:
- Click on "Delete Cookies" (click OK)
- Click on "Settings" and change the "Amount of disk space to use:" to something between 64MB and 128MB. (It may be MUCH larger right now.)
- Click OK.
- Click on "Delete Files" and select to "Delete all offline contents" (the checkbox) and click OK. (If you had a LOT, this could take 2-10 minutes or more.)
- Once it is done, click OK, close Internet Explorer, re-open Internet Explorer.

You can use an application that scans your system for log files and temporary files and use that to get rid of those:

Ccleaner (Free!)
http://www.ccleaner.com/
( just the disk cleanup - don't play with the registry part for now )

Other ways to free up space..

SequoiaView
http://www.win.tue.nl/sequoiaview/

JDiskReport
http://www.jgoodies.com/freeware/jdiskreport/

Those can help you visually discover where all the space is being used. Then you can determine what to do.

After that - you will want to check for any physical errors and arrange everything for efficient access"

CHKDSK
How to scan your disks for errors
* will take time and a reboot.

Defragment
How to Defragment your hard drives
* will take time