I may have contracted a virus

A full startup disk would cause most of the symptoms you describe.

There aren't any known malware that can infect your fully up-to-date Mac unless you allow people access to it, either directly or remotely, and they install something.

You can scan for Adware which you may have inadvertently installed using this: http://www.adwaremedic.com/index.php

Or manually via Apple's article: Stop pop-up ads and adware in Safari - Apple Support

Hello Peter Kertesz,

I understand you are experiencing erratic or unresponsive behaviour with your MacBook Pro, and you believe this is being caused by a virus. However, I think it may be related to the warning messages you've been receiving that your start up disc (internal hard drive) is full. So, I'd like to provide you with some basic troubleshooting steps for that issue first.

Your profile above doesn't include your MacBook Pro. What version of the operating system are you running on it? If you have not already done so, I would suggest you purchase an external drive and make a Time Machine backup of your hard drive.

Use Time Machine to back up or restore your Mac

Then, check to see how much space you've used your computer, and how much is available to use. To free up space, copy files from your MacBook Pro to your external drive. Make sure you can open them from the external drive, then delete them from your MacBook Pro and empty the trash.

OS X: What is "other" space in About This Mac?

The "About This Mac" window displays an estimate of how much space certain files are using on each of your drives.

To view Storage information for your connected volumes, select About This Mac from the Apple menu, then click the More Info button in the window that appears. Next, click the Storage tab to display storage information

Sometimes the "Other" category in the About This Mac window may seem large. About This Mac uses this category to count any files that aren't recognized as one of the other listed file types (audio, movie, photos, apps, backups). Examples of files that may be calculated as "other" include:

Freeing up disk space

If you need to increase the amount of available disk space on your startup drive, examine the items in your home folder. Look in the Documents, Downloads or Desktop folders to see if there are any files you don't need anymore. Use these suggestions to reclaim disk space from these folders:

• Delete items you don't need, or have copies of elsewhere, by dragging them to the Trash.
  Once you're sure you don't need the items in the Trash, empty the trash to reclaim disk space. From the Finder, choose Finder > Empty Trash.
• Move items to another drive, such as an external hard disk or flash drive.
• Compress items you don't use frequently. Delete the originals of these files and keep the compressed copy instead.

Be sure to only delete items you no longer need, or have copies of elsewhere. It's a good idea to create backups of important files in case you accidentally delete an important item later.

OS X El Capitan: Increasediskspace

See if the issue is resolved when you've freed up some resources on your computer. If not, I'll include some additional troubleshooting resources for you below:

Try safe mode if your Mac doesn‘t finish starting up

Starting up in safe mode

Follow these steps to start up into safe mode.

1. Start or restart your Mac.
2. Immediately after you hear the startup sound, press and hold the Shift key.
3. Release the Shift key when you see the Apple logo appear on the screen.

After the Apple logo appears, it might take longer than usual to reach the login screen or your desktop. This is because your Mac performs a directory check of your startup disk as part of safe mode.

To leave safe mode, restart your computer without pressing any keys during startup.

Use Activity Monitor on your Mac

Activity Monitor shows the processes that are running on your Mac, so you can see how they affect your Mac's activity and performance.

Peter, I hope these initial steps will get you on the path to a more responsive computer. If you are still having trouble, please reply to this post after completing the steps above, and let us know the results.

Take care,

(My computer's photos is backed up on Dropbox, so I will begin deleting photos from my laptop, to ease up the local memory)

You are referring to the space on your hard disk. You need to maintain an absolute minimum of 10 - 15 GB for the OS to operate properly. Memory is the RAM you have installed.

FWIW, your profile shows you are on 10.4.10? Is that correct?

And, before deleting anything on your hard drive, make sure you have a backup just in case.

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