Q: After installing El Capitan my Mac is takin almost 5 minutes to boot up.

Please download and install EtreCheck from http://etrecheck.com/

Run it and post the report here.

Please take each of the following steps that you haven't already tried. Test after each one. Back up all data before making any changes.

1. Set the default startup disk.

2. Disconnect all wired peripherals except those needed to start up. If there's no change, reconnect them

3. Reset the System Management Controller.

4. Reset the PRAM. Afterwards you'll need to repeat Step 1.

5. Reset the printing system.

That well may be normal for the first boot after installation. First, it is setting up certain system files. Second, Spotlight is indexing the disk. These will slow down the computer until finished. After that it should run normally. If that isn't the case:

Ways to help make a slow Mac faster

 

1. 17 Reasons Why Your Mac Runs Slower Than it Should
2. Slow Mac Performance? This Article Solves It!
3. Fix slow start-ups in OS X | MacFixIt - CNET Reviews
4. How to fix slow shutdown and startup times. | MacTip.net
5. 6 Easy Tips to Speed Up OS X Yosemite on Your Mac

 

Avoid using third-party cleanup software. Usually this software does more bad than good. You don't need it. All computers become slower over time even under normal use. Experienced users erase the hard drive and do a clean install from scratch from time to time; or whenever installing a major OS upgrade. Doing so means you must maintain regular and multiple backups.

 

Add more RAM or cut back on the number of concurrently running applications and utilities. Remove unnecessary anti-malware software and any software that promises to clean your Mac. Check for runaway processes: Runaway applications can shorten battery runtime, affect performance, and increase heat and fan activity. Also, visit The XLab FAQs and read the FAQ on dealing with The Spinning Beach Ball of Death.

 

The Ultimate Fix

Backup everything, erase the drive, reinstall OS X, and restore your data from the backup. Reinstall third-party software from original media/scratch.

[Permission to use part or all of the above has been granted by Kappy, exclusively, to theratter.]