If your QuickBooks is running slowly, it might pay to look at your anti-virus software. Good anti-virus software is critical to a secure computer system. The problem is that freeware tends to scan every file when opened as if it is an email with potential viruses.
This is fine until you start working on a network with large QuickBooks files. Every time someone looks at a customer or invoice, his or her virus software scans every record in the file. If two people are using QuickBooks, they can both be scanning the same master files at the same time. That can really slow you down.
Some virus software is designed to work on a network, and lets you exclude certain files when opening them. Remember all of your files should be scanned on a daily basis.