Slow Windows Updates and "Checking for updates..." hangs are a common problem for many Vista SP2 users these days. Microsoft has not released a permanent fix (and I doubt they will before extended support for Vista SP2 ends on 11-Apr-2017) but there is a temporary workaround that was first posted at http://wu.krelay.de/en/ by a German blogger named Dalai. This workaround requires Vista SP2 users to pre-install a new Windows kernel-mode driver (Win32K.sys) update each Patch Tuesday (the second Tuesday of the month) to speed up Windows Update.
Please see the step-by-step instructions posted on page 1 of m#l's thread Updates not working, it has been searching for updates for hours in the MS Answers forum (I post in that forum as user Great White North). As of 08-Nov-2016, there are now six Win32K.sys updates that need to be installed to speed up Windows Update on a Vista SP2 machine: KB3078601 (rel. 18-Aug-2015); KB3109094 (rel. 07-Dec-2015); KB3185911 (rel. 13-Sep-2016); KB3191203 (rel. 11-Oct-2016); KB3198234 (rel. 08-Nov-2016); KB3203859 (rel. 08-Nov-2016). Note that users only need to install the Win32K.sys updates in this list that are currently missing from their system, and this list of speed up patches will be revised after the December 2016 Patch Tuesday updates are released on 13-Dec-2016.
There is one possible alternate solution that I haven't tried myself, but a few users have reported some success using Torsten Witrock's WSUS Offline Update tool to patch their Vista SP2 computer. User Ed posted in the AskWoody.com thread How to update Vista quickly? that this tool can also be used to patch Vista SP2 if users select the Legacy Products tab on the interface. The FAQ for this tool can be found at http://trac.wsusoffline.net/browser/trunk/doc/faq-enu.txt.
EDIT:
...and if you try Dalai's workaround, please note that "speed up" is a relative term. You have a 32-bit computer with only 2 GB of installed RAM, and depending on the last time Windows Update was able to successfully install updates on your system, your manual Windows Update in STEP # 6 of the instructions could require anywhere from 1 to 9 or more hours to run to completion.
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32-bit Vista Home Premium SP2 * Firefox v50.0.2 * NIS v22.8.1.14 * MBAM Premium v2.2.1
HP Pavilion dv6835ca, Intel Core2Duo T5550 @ 1.83 GHz, 3 GB RAM, NVIDIA GeForce 8400M GS