after my computer has started up and loaded it throws up a diaglog box with the following messge:

The Application OR DLL C:\WINDOWS\SYSTEM32\WINSRC.dll is not a valid windows image. Please check this against your installation disc.

i don't have the installation disc so can i just locate this file and delete it?

Before doing anything drastic, I recommend you purge your system of clutter using Windows (XP or Vista) Disk Cleanup, ATF Cleaner or CCleaner. If you use CCleaner, then during installation, uncheck the option to install the Yahoo toolbar and before first use, go to Options > Settings > Advanced and ensure Only delete files in Windows Temp folders older than 48 hours is unchecked.

Note: Ensure you know your site credentials (user name and password) for sites you frequent before cleaning; you may have to login again at next visit.

Then download, install, update, and run Malwarebytes's Anti-Malware (MBAM) to ensure your system is free of malware. Then do the same for all other computers on your network (everything on your side of the Internet gateway, typically a cable/DSL modem).

If it finds anything, you will need to re-evaluate your current security.