Please note that this hack is only applicable for Firefox users. I have not yet able to play with IE nowadays.. 
METHOD 1:
This method requires modifying User Agent string of firefox about config
1) Type about:config at firefox address bar
2) Search for general.useragent.extra.firefox
3) Double Click on it
4) Change default value to MEGAUPLOAD 1.0 (if your version is 3.0, change it into MEGAUPLOAD 3.0)
That’s it, now start downloading from Megaupload without download slot limit restriction.
METHOD 2:
This method uses User Agent Switcher Firefox Add-on Download and Install
1) Now go to Tools – User Agent – Options and enter following value
2) Description: MegaUpload
User Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; Alexa Toolbar)
3) Save these settings
4) Now Access User Agent Switcher from Tools and change user agent setting to MegaUpload.
2) Description: MegaUpload
User Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; Alexa Toolbar)
And start downloading from MegaUpload without any Dwonload Slot Limit.
METHOD 1:
This method requires modifying User Agent string of firefox about config
1) Type about:config at firefox address bar
2) Search for general.useragent.extra.firefox
3) Double Click on it
4) Change default value to MEGAUPLOAD 1.0 (if your version is 3.0, change it into MEGAUPLOAD 3.0)
That’s it, now start downloading from Megaupload without download slot limit restriction.
METHOD 2:
This method uses User Agent Switcher Firefox Add-on Download and Install
1) Now go to Tools – User Agent – Options and enter following value
2) Description: MegaUpload
User Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; Alexa Toolbar)
3) Save these settings
4) Now Access User Agent Switcher from Tools and change user agent setting to MegaUpload.
2) Description: MegaUpload
User Agent: Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1; Alexa Toolbar)
And start downloading from MegaUpload without any Dwonload Slot Limit.
