By definition, a portable application is a program run from a removable storage device that leaves no personally identifiable information behind in the host operating system. In other words, someone crawling through a system that you recently used a portable app on, should not be able to find any traces of data in the file system or registry any more damning than the simple fact that someone ran an application. That's it. No cookies, cache files, preferences or saved data should ever touch the machine's hard drive, and if they do, they must be securely overwritten prior to the ejection of the removable media. There are three main platforms for running a portable application from a flash drive - U3, PortableApps.com, and Ceedo.
U3, first brought to market in 2005 by San-Disk, is the oldest and best known of the three, appearing in almost all of Sandisk's flash drives since it was launched. U3 works by mounting a virtual CD-ROM drive in addition to the main storage partition. The virtual CD-ROM would then trigger Windows' Autorun and execute a "LaunchPad" in the System Tray to provide quick access to applications and data housed on the flash stick. Optionally, the storage partition could also be made completely inaccessible to the host computer unless first unlocked by the LaunchPad utility, though this only works on Windows machines.
While U3 initially showed promise and a strong showing of support from major software developers such as McAfee, Skype, Trillian and others, the platform eventually decayed due to a lack of public support and a large amount of neglect. Users quickly became frustrated with the system for the long load times and perceived intrusive nature of the LaunchPad, along with the use of two drive letters. Two drive letters meant that on some systems the data partition wouldn't show unless you fiddled with the Disk Management utility, and it also meant that many embedded systems such as photo kiosks would not recognize the drive.
Today, the U3 Software Central portal is flooded by a sea of trialware and crapware, with many of the U3 app vendors offering portable counterparts that will run on generic non-U3 drives. Moreover, several of the top downloaded applications on the U3 portal like those from Mozilla are hosted on RapidShare accounts and point to outdated, insecure versions that were released over a year ago and contain many bugs. Automatically updating these to a newer version would sacrifice the portable app's nature such as personal files no longer being kept secure. In 2008 it was revealed that San-Disk and Microsoft were working on a successor to U3 called StartKey, though no new news has been released on that front.
PortableApps.com is the primary competitor to U3 and our personal favorite here at Everything USB, offering a platform similar in appearance to U3 that can be run from any flash drive. The strongest bit of appeal for PortableApps.com is the myriad of free and open source software that's available for the platform. Everything from the latest versions of Firefox and Thunderbird to popular games, IM clients, office applications, media players, server software, and antivirus clients can be had here for free. Best of all, the platform is frequently updated with patches and new applications are being added all the time.
The brains behind this magnificent operation is John Haller, the creative genius who's also behind the almost-parody site MAFIAA.org, exposing the film and music industries as the organized crime syndicates we know they are. Many of the behind-the-scenes tweaks to make applications "portable" such as file locations, limited writes to increase flash durability, plugin compatibility, etc., are carried out by John, who not coincidentally was also responsible for the developing the U3 version of Mozilla Firefox before it was taken over and neglected by U3 LLC.
Ceedo is the most unique of the bunch, available for all flash drives and utilizing its own portable application directories and registry hives to essentially envelope and host applications that weren't originally designed to be portable, e.g. Adobe Photoshop. Like the competing U3 and PortableApps.com suites, Ceedo too sports a launcher for quickly accessing files and portable applications, appropriately themed after the Windows XP Start Menu to accommodate the large amount of software that can be installed with it. Ceedo is currently at version 3.1 and has expanded their Argo technology to support .exe, .msi, and .msp installers, a significant upgrade from Ceedo v2.0 which was reviewed by us in 2006.
While Ceedo has the clear advantage when it comes to application compatibility, it does have a few drawbacks that must taken into consideration. First off, it understandably does not work well with applications that require their own services, and certain apps may require the use of admin privileges on the host computer. Second, as of this writing, Ceedo is currently incompatible with all 64-bit versions of Windows, leaving behind a large number of Windows 7 users or anyone with 4GB of RAM installed. Ceedo mentions on their website that a 64-bit version is currently in the works as a closed-beta. Finally, Ceedo costs money and requires activation. While we personally believe that the $39 asking price is more than reasonable, it's easy to see why the adoption rate might not be as high as PortableApps's free offerings and Sandisk's "free" U3 platform. In any case, we suggest you take Ceedo's free 30-day trial for a spin before you write it off. s