You do not indicate if this is a Branded System or White Box
As most Brand Name PCs are shipped with a set of Restore CDs [with few exceptions] we can safely presume this is a small volume build white box
There should be a Restore Disk set [on Floppy Diskettes] which you will need for this process. These will have all the files required initially and load some form of Window [even if DOS like] to guide and prompt you throught the rebuild process and as part of the creation or set-up process, it should automatically point to the file on the D Drive. From memory the Application that creates a PQIMAGE file is called Drive Image - from PowerQuest [now part of Symatec's empire]. It is a compressed file
When using this, you will effectively wipe out all of your C Drive and be left with the original delivery configuration of your system. It will not of of course have all you personal system settings or data saved, unless you have created a recent Image file.
I would recommend that you use the Files and Settings Transfer Wizard to save all your current files. This will create a unique file, that you can save to Hard Disk [D Drive if you have enough space or else C drive and burn off to CD]. It can then be used after rebuild to reinstae your personal files and setttings after you install any applications etc that you have installed since buying the PC
If you do not have the Restore Disk set, you can contact the manufacturer of the PC, or try to download from their website, or else call Symantec
good luck