1. Unlock the Evo for free - if you are good with tech stuff
2. Buy an unlock code for the Evo - easier, but still requires some tech smarts
3. Buy an unlocked Evo - no tech skills required

1. Unlock the HTC Evo 4G for Free

If you have Windows, you can download a free application that will root and unlock your Evo for free. It's called Simple Root, and Lifehacker reports that it works very well.

Pros: It's free! Also, it roots the Evo as well as unlocks it. This can cause problems down the road with upgrades, so this is also a con.
Cons: There are a few cons, because this is the riskiest of options.

• No tech support if something doesn't work or goes wrong
• It could screw up your phone. A lot.  As Lifehacker puts it:
  

  Simple Root is a free download for Windows systems. As with all rooting or firmware-modifying tools, be aware that bad things can happen, and you should make backups where you can.

• You must already have bought an Evo.

2. Purchase an unlock code for the Evo 4G

If you're intimidated by the tech-heavy and potentially phone-fatal Simple Root option, you can purchase an unlock code. You can purchase an unlock code from UnlockedCellPhoneCode.com for $34.99.

You will be asked for a few pieces of information: your cell phone's IMEI (found inside the battery compartment, can be found by dialing *#06# on your phone), the phone model, and your current carrier.

UnlockedCellPhoneCode.com will then email you with a code that you enter into your cell phone. Once you do, your phone will be unlocked and able to be used on other carriers.

Pros: UnlockedCellPhoneCode.com offers 100% refunds if your unlock doesn't work. They also offer support if you have questions while unlocking your phone.
Cons: You still will have to do some technical things, including entering in codes into your Evo 4G. This also requires you purchase a phone before attempting.

3. Purchase an already-unlocked Evo 4G

If you don't want to have to deal with all the possibilities for failure and for ruining your brand new Evo, you may want to have someone else unlock your phone before you even buy it.  Buy the phone, put in your SIM card, and know that everything will work properly.

Pros: The Evo 4G is already unlocked and ready to use with an alternate network. Purchases from eBay are backed 100%: if the phone isn't what they said it is, you'll get your money back. (read what eBay/PayPal's buyer protection policy is)
Cons: Unlocked phones are more expensive than phones that come with your carrier's plans.

If you already own a 4G...

If you own an Evo, you should try options 1 or 2 - that way, you won't shell out of pocket for another phone.

If you haven't yet bought a HTC Evo...

If you're considering buying an Evo 4G, but you don't own one yet, then all options are on the table.

If you're tech savvy, try unlocking it yourself and same some dough. If you'd rather have it ready for you, you can find good deals on unlocked HTC Evo 4G on this website.

Have you tried unlocking your Evo? Tell us how it went.

Have you already attempted to unlock your HTC 4G? How did it go? Success, or brick?

The HTC Desire models are all the same...except the frequencies they use.

If you're shopping for an unlocked HTC Desire, you may be wondering what the differences are between the three models available: the a8181, a8182 and the a8183.

Each of them has the same operating system (Android 2.1 Éclair with HTC Sense™), processor speed, memory etc -- they are identical in every way except for the supported networks.

Even an unlocked HTC phone needs the right wavelengths.

Make the carrier you want to use supports the model Desire you're buying. Example: all three phones will work with T-Mobile, but none will support T-Mobile 3G.

HTC Desire a8181

HSDPA/WCDMA: 900/2100 MHz
Quad-band GSM/GPRS/EDGE: 850/900/1800/1900 MHz

HTC Desire a8182

HSDPA/WCDMA: 850/1900 MHz
Quad-band GSM/GPRS/EDGE: 850/900/1800/1900 MHz

HTC Desire a8183

HSDPA/WCDMA: 850/2100 MHz
Quad-band GSM/GPRS/EDGE: 850/900/1800/1900 MHz

Call your carrier to confirm compatibility.

Nothing is more frustrating than buying technology that isn't compatible with your plans. Call your carrier to make sure the phone will work.

Update: a8182 has a different display type.

bfksc on HTCForums.com clarifies another difference between models:

Another difference is the display type. In the 8182 I have for N/A market is an S-LCD display instead of the Super-AMOLED. Other than that, and branding for Telus, the phone hardware is identical. I should also mention that the Telus branding also disables the EDGE/GPRS data because Telus and Bell do not use it - stupid move since that means all US/CDN travellers going to EU will not have data since the freqs are different for 3G and 2G data is disabled.

However, there is a way around that by unbranding and updating to Froyo 2.2 which will remove the block for EDGE/GPRS and offer more features.