By default a 3750 will do no routing. To enable routing on a 3750 you need to enter "ip routing" at the global configuration mode.
Even if you are running IP routing on it, you can still create a L2 network, just go to global config and type "VLAN 27" and VLAN 27 is created.
You can even set the IP address and make it an SVI (switched virtual interface) on VLAN 27, as long as none of your end users are trying to use the SVI IP as a default gateway, and you have proxy-arp disabled, this switch will do no routing, and you can use the IP address to remotely connect and manage the switch.
If all you want is to use this switch as a Layer 2 device, then just create your VLANS and assigned interfaces to your VLANS using the commands :-
switchport access vlan x
switchport mode access
no ip address
snmp trap link-status
where x is your vlan.
Then add these VLANS to your trunks to other switches and have the Layer 3 drop elsewhere.
Just do not create any SVI 's with IP address attached or allocate any IP's to physical interfaces.
Sorry all I forgot to mention that the switch is being used as a L3 switch for other servers, the L2 VLAN needs to coexist, so as long as the VLAN doesn't have an IP address then all ok?
Adam is correct unless you create layer 3 SVI's then it is a layer 2 switch , even if routing is turned on if there are no SVI's created on the 3750 other than the mgt address then it is basically a layer 2 switch.
Thanks, it already has SVI's on it for other servers, I beleive if I create a VLAN with no IP it's a L2 VLAN?
Don't worry about the other SVI's just do not create any for the new VLAN you are going to build out and all will be good.
"Thanks, it already has SVI's on it for other servers, I beleive if I create a VLAN with no IP it's a L2 VLAN?"
That is correct.