SandiTank - I hate to break this to you BUT "Virginia, THERE IS NO XAMPP". What there is is probably 20 people, all unpaid volunteers who make all this stuff work. The developers who make the compilations, and create the configuration files and 'packages' and the volunteers (like ourselves) who answer the questions. DItto (except larger numbers) for Apache, PHP, Perl and the rest of the pieces that make up XAMPP. Collections of people (very few of whom get paid).
Say what you want - go off the rails or whatever - XAMPP isn't a company or anything you have probably thought of (well, clearly not much thinking has been used so far). And, at the moment, you are pi&&ing off the only people who can help you. Altrea, myself and Sharley are 'the masters of this domain' - Note the "AF Moderator" next to Altrea's name (and mine) then cruise down to the bottom of the index and note that Green means Global Moderator - how do you think that got there??? Must have been "XAMPP" huh?
And HERE is the first real problem -
my website has around 10,000 visitors daily and at certain moments it reaches 500 at the same time.
Read the FAQ, XAMPP is not intended for a production environment. You chose the wrong tool, fool.
The default configuration is not good from a security point of view and it's not secure enough for a production environment - please don't use XAMPP in such environment.
If you want guaranteed response time, and on-demand support save your Euros and buy a commercial distribution of a server product or hire a consultant (like me -- that's what I do). Otherwise, follow the rules, post the OS version correctly and decide to wait your turn for the free hand-outs (as that is what this is).
A final parting note (which may explain things) and is totally free (just like the XAMPP download you didn't pay for).
IF you are actually running Windows 7, which is a DESKTOP operating system, at the volume you are at, you may well have run into an engineered speed bump. I suggest you look in the Event Viewer. <== hint it might not be an XAMPP issue. I certainly don't know this to be 'for sure', but you say you don't have errors in the error log. You may also have run into hardware or 'pipe size' issues, at 500 concurrent users you need a VPS in a server farm, not XAMPP in your dairy shed.