jeffp -

If the computer runs to your satisfaction and you'll never connect to the internet, there's relatively little need to upgrade; but you should consider that the internet isn't the only source of infections. Any method you use to load programs/files or to offload them to any other machine can be a way of transmitting malicious code.

An infected recording that you edit could deposit something that would become part of the next recording you edit, thereby passing the infection to the next machine that plays the recording.

Historically, most "business office" infections not too long ago came from someone "playing a game" brought in on a floppy disk (long ago) or more recently on a memory stick. (It used to be called a "sneaker net connection.") The method has been used quite recently - with the mysterious virus designed to attack uranium concentrators made by a specific company and sold to a particular country being "input" (it's said) via a flash drive "innocently" given to "someone" with access to the network that controlled the refining facility. The infection could have been hidden in a new version of PacMan(?).

Windows 7 advertises improved ability to run "legacy programs" but it's not clear (to me) whether it's the same "virtual machine" method used in Vista or possibly something slightly different. This is one of the features that, in Vista at least, was NOT AVAILABLE in the "Home Basic" versions supplied with many machines, but available to those who got the "Home Premium" or higher versions or who upgraded. I've seen little feedback on how well it has worked for people who have an appropriate Win version and tried to use it.

For reference: Another possibly significant thing omitted from the simplest (cheapest) recent Win versions is the utility for making a full Recovery Disk for System Backup. There are other ways of doing this, and I've never seen a Microsoft Backup that restored anything, so it may not be too important.

Microsoft has web sites where you can look up whether a specific program has been "verified compatible" to either Vista or Win7; but only programs tested by Microsoft or reported by the program builders are likely to be listed, so most programs I've tried to check on have been "missing" in the lists. Several older programs that Microsoft says are not compatible do, in fact, run adequately on my Vista. About the only way an individual has of being reasonably sure is to try to run the program on the OS, although those certified as compatible are a fairly safe bet.

John