IMO, I would never want to connect my system to known infected computer...unless I'm pretty sure of two things:
a. My system is well-protected...and I have backups since protection is an after-effect of new malware. I want to be prepared for a possible delete/clean install operation, just in case my defenses are lagging whatever may have infected the other system.
b. I don't mind it if I have to do a clean install. I know how to do such and I have everything I need to effect such.
That was the approach I used last year when I decided to try to clean a couple of infected systems for a friend. I'm not in the business, I'm just a user, with two systems in my apartment
<<My son's computer, in another room, has sort of crashed.>>
That's not a very descriptive statement, since "crash" means different things to different users. It obviously boots or you would not be ccntemoplating obtaining any info from it.
Exactly what are the symptoms of it malfunctioning? Can you boot into safe mode? Does it boot normally into XP?
Any onscreen error messages?
System manufacturer and model?
As for connecting to provide info about the system...if it boots, just connect to the forum from that system. If it doesn't boot, you can remove the hard drive and connect it to another system...and thereby obtain certain info that may be useful.
The more pertinent info concerning the circumstances...the better suggestions can be made. Remember...we cannot see this system, while you can