Generally disk doctor does not fix anything related to viruses, trojans, etc. It, on a PC at least, potentially fixes errors in the system directory, moves data out of bad disk sectors, sometimes repairs bad disk sectors.


If your computer is slow when not using the internet, do as Bob suggested and run the disk utility he mentioned. This will show you what processes are running and how much of the processor they are using. If a process looks weird, you can do an internet search for the process to find out if it is a virus, trojan, malware, etc. Running a virus scan will hopefully find these things as well, but not always.

No, if by disk doctor you mean the Disk Utility and running Repair Disk Permissions, then no, that will not scan for viruses.

You can check the free space on your hard disk, by right clicking on the "Macintosh HD" icon and selecting "Get Info" (or, left click once on the icon and press Command-i). Under the "General" section you'll see "Capacity" and "Available". If your available space is <10% of Capacity, consider removing old stuff (there are programs out there than can clean up caches and unused files).

If you really want to look for viruses on a Mac, I would suggest starting with ClamXAV. It's free, but the viruses id's get updated frequently. The interface isn't as pretty though. www.clamxav.com/ Note that this WILL likely find viruses in your email, especially if you save an store email messages using Mail.app or Entourage.

HOWEVER.

The viruses it finds will be for Microsoft Windows, and not Apple's OS X. They are not binary compatible, so the Windows viruses cannot infect a Mac, but they can reside on your system innocuously (until you forward that email to a friend with windows). Also, since you're running 10.3.9, I'm guessing you're on an older, slower, PPC Mac (G4 or G3) which uses an entirely different processor, with entirely different instruction code. A virus created for an Intel system would not be able to run natively on that processor.

The reason I say it's unlikely that it's a virus is that there just aren't really any viruses for OS X. Security concerns, yes (usually fixed in patches by Apple). Trojan horses, maybe.

Which is why I suggested looking into other paths first. If your disk is over 90% (or even 80% I've heard) full, it can affect performance. This is because of the virtul memory system. Virtual memory allows the system to address more memory space than it actually has. It does this by allocating space on the hard drive to write 'pages' of memory (parts of programs or large files) out to the disk, and read them back when it needs them.
If you're using programs that take up much more memory than your system has, like if you're running photoshop on a system with 512 MB, then your system will spend a lot of time writing and reading those pages. This is called 'thrashing'.

The reason I mention flash is that you don't need to be connected to the internet or even viewing a flash page any longer for flash to take up (a lot, I mean a LOT) system resources (namely, CPU time). All your web browser has to do is load the flash engine ONCE (say for a banner ad - which most banners are now), and even if you close the page/tab where that flash was, the engine keeps running, and keeps taking CPU time. So, even if you're no longer connected to the internet, you'd need to quit the web browser to kill the flash engine.

So, yeah. I just kinda doubt it's a virus. :)

I'd like to add my support to Jory and Mr. K. My PowerMac G4 was a 2000, and was an OS 10.3.9. When the power supply finally died on it in July, Melrose Mac was calling it a "vintage" Mac. It would have cost close to $1000 to get that machine up to speed, so I got a new iMac instead ($1300 with AppleCare Support). Now, if I had been religiously backing up on my EHD like I had been planning to, I would not have had to pay them to move data from the dead computer to my EHD. But I didn't, so I got dinged with $225 for that. So yes, start backing things up now, every day. Because your buddy could be on his last legs.