Switch has to buttons: Reset and Clear. You can see it on the photo below.
To delete actual configuration you have to:
- push and hold button Reset (for more then 1sec)
- push and hold button Clear (for more then 1sec)
- release button Reset (wait till Test LED begins to blink)
- release button Clear

After that there wil be no password in CLI.
 

ROM information:
   Build directory: /sw/rom/build/nemorom(ndx)
   Build date:      Nov 28 2007
   Build time:      16:36:54
   Build version:   R.10.06
   Build number:    14201

OS identifier found at @ 0xbc020000
Verifying Image validity ...
CRC on OS image header Passed
CRC on complete OS image file Passed
Valid OS image @ 0xbc020000

Decompressing...done.
CRC of image is 0x9f03940e 
CRC @ 0x80001000 Len 10102672 is 0x9f03940e



initializing..
ROM information:
   Build directory: /sw/rom/build/nemorom(ndx)
   Build date:      Nov 28 2007
   Build time:      16:36:54
   Build version:   R.10.06
   Build number:    14201






ProCurve Switch 2610-24# show running-config 

Running configuration:

; J9085A Configuration Editor; Created on release #R.11.07

hostname "ProCurve Switch 2610-24" 
snmp-server community "public" Unrestricted 
vlan 1 
   name "DEFAULT_VLAN" 
   untagged 1-28 
   ip address dhcp-bootp 
   exit 

ProCurve Switch 2610-24#