here is a simple guide :

http://www.unrevoked.com/rootwiki/lib/exe/...-usb-driver.zip
http://shipped-roms.com/shipped/Buzz/RUU_B...2190_signed.exe

1. boot into hboot (volume down + power)
2. now device manager >> Other Device - Android 1.0
3. right click Update driver software >Browse My Computer For Driver Software> choose Android USB Driver( the file u just extract)
4. u will see Android Bootloader Interface under Android Phone in Device Manager
5. restart yours phone
6. enavle USB debuging
7. in device manager u will see ADB under Other device
8. right click select Update Driver Software>Browse My Computer for Driver Software>Let me pick from a list of a device drivers on my computer>android phone>Android ADB Interface
9. after install complete u will see Android ADB Interface under Android phone

10. Download and run the exe file. (attach usb to phone with USB debugging)
11. On the Welcome screen, click Next to begin the RUU installation.
12. Check the listed instructions in the dialog box and make sure you have done them. Click Next to proceed.
13. A message will then be displayed indicating that the utility is verifying and acquiring information about the Android phone as preparation for the update process. Wait for this verification process to be finished.
14. After the verification process, current information about the Android phone will be displayed. Click Update to proceed.
15. Information about the current image version and the new image update version will be displayed. If you are sure that you want to install the new RUU, click Next to proceed.
16. A confirmation message will appear and show the time it will take to install the necessary files (including radio image) to the Android phone. Click Next to begin the update. A progress bar will run through the screen during the update process.
17. RUU update is complete. Click Finish to exit the utility.

after complete yours phone software version will be 1.25.707.1
now u can check for froyo update
new froyo version will be:

Android Version:
2.2.1

Baseband Version:
13.55.55.24H_3.35.20.10

Kernel Version:
2.6.32.21-g6c55ee4

Build Number:
2.24.707.1 CL298423

Software Number:
2.24.707.1

try this..
make sure youre connected to HTC sync

hmmm i think u need to reinstall your driver... mine no problem... installing... almost 70% done... waiting for froyo...
yes and no... most important my contact is still there... hopefully and i back up partial of my msg thru a back up system...