Compaq (now HP) doesn't actually make hard drives...they purchase a Maxtor, Seagate, Western Digital, etc. just like anyone else and install it in their machines. Thus, any will do, provided it uses the same interface (PATA vs SATA) and is the same size format (2.5in vs 3.5in).
Hope this helps,
I have a Compaq Laptop V6420US and would like to upgrade the original 80GB hard drive with something like...200GB. Do I need to purchase a specific type of Compaq or HP hard drive or will any notebook hard drive from Fry's, Best Buy, ect. work just as well ?