Nowadays we all have so much information on our hard drives that it’s really hard to find a document or an e-mail that you need right now. Yes, sure you remember it was somewhere here: in this folder, or… maybe in that? Oh, wait, you have copied it recently somewhere else just to put everything in order. And now you are stuck… Stuck with hours of searching your hard drive and guessing where that damn specification is…
Ladies and gentlemen, please meet our best friend - desktop search engine!
Desktop search application is a piece of software which helps searching for different type of data through virtually any type of files and documents residing on your hard drive, or even on different network locations you have access to. It is kind of Yahoo! or Google running locally 
Why do you need desktop search engine
Just an example: after four years of working in one company I have accumulated several thousands of e-mails in my Inbox folder. And almost the same amount of them in my Sent folder. All of them were from either my manager or a third party partners, and all of them had very useful information explaining different details of projects we were working on. The main problem was that from time to time I had to find an e-mail with all the details about one particular problem in order to understand what a prehistory of the issue was or how it was fixed… Using standard F3 search in famous e-mail client application in this case takes way too much time and often does not bring desired results…
Once I’ve installed desktop search engine on my PC and it had indexed my hard drive (which took just one night actually), I was able to search for any text patterns through out my e-mails and even within PDF attachments in them! This is besides of default capabilities of such a software to perform a search through standard document files like TXT, DOC, XLS etc.
Another example: imagine you have a software project with 20-30 MB of source code files. You work a lot with this project and have to search through out of it very often. Using standard “Find” functionality of a development environment can be not that fast at all. Need to find a class or structure usage, or a specific function call in all possible situations in the project? No problem, just call your desktop search program and you got it!
What I like about desktop search software is, it brings the result instantly!
How desktop search engine worksUsually such programs have two parts installed on a PC: a service and a client application. The service’s task is to work as a background process on your computer and create an index database - this is a database which keeps track of all documents and files (and words in them) the service has found on your hard drive. This indexing process might be pretty long before the whole content of the hard drive is indexed for the first time. It can be a couple of hours or a couple of days - depending on how much data you have. But all this is done in the background, and usually during system idle time (when you do not use it).
The client application is a program for a user. It allows to specify what text pattern should be found, in what file types, or in e-mails etc. and, of course, it displays search results at the end. The program uses only the index database to search whatever the user is looking for. But this search is very fast by its nature.
Google Desktop Search vs Copernic Desktop Search
There are plenty of desktop search software products our there. And a good news about it is there are many free products! Just download, install and use. But you must be careful choosing them and understand what to look for.
I did not had much time to try everything available on the market, so I went first for the leader in the search industry - Google Desktop Search (GDS). At the beginning it was great: the same look and feel if I’d search using Google itself online! Also it was fast and even attempting to display search results while I was typing a search text in its integrated into taskbar edit box. But two days later I’ve discovered very unpleasant thing: GDS did not “find” a text fragment in a document while I saw the text there and the indexing was completed. As it turned out GDS has a super feature: it does not index large documents (DOC, PDF, or whatever) after first ~100KB of data. I had many spec documents with size of 400…600 KB and I could not search them in full! And I did not know it at the beginning and hence was confused a lot not having expected results. That indexing limitation was too much for me - GDS was uninstalled right away. (I have no clue if they had fixed or made configurable that 100KB “feature” since that times, Sept. 2005).
Then I gave a try to Copernic Desktop Search (CDS) program as one of most popular software products in this sector. Before installing the program I had asked Copernic Support about GDS problem and they proudly replied: they do index files in whole. That was what I needed. CDS has it’s own UI which is not bad either. Once you used to it, it’s friendly enough. The indexing takes also pretty much time, but then after it indexes all new file, documents and e-mails on-the-fly and you have not to take care of that.
After CDS I even do not want to recommend you anything else. 
Desktop Search and Security
When choosing desktop search solution for your needs consider one important thing - security. Especially this is important if one PC is shared by several users. The problem is, the indexing service (if run under system account) can be able to index all files and documents regardless of their ownership. So, finally, performing a search within your e-mails you may be able to see emails of other users!… Well designed DS programs must handle these cases without problems, so be aware. Google desktop search is not one of them. Some companies even restrict access to its home page for their employees to prevent GDS from being installed and used at work.
and can support this project by making webstores and portals for my customers in parallel.